diff --git a/src/pyj/ajax.pyj b/src/pyj/ajax.pyj
index f6cead2cf3..ec2d8db838 100644
--- a/src/pyj/ajax.pyj
+++ b/src/pyj/ajax.pyj
@@ -4,6 +4,17 @@ from __python__ import hash_literals
 
 from gettext import gettext as _
 
+def encode_query_component(x):
+    ans = encodeURIComponent(x)
+    # The following exceptions are to make epubcfi() look better
+    ans = ans.replace(/%2[fF]/g, '/')
+    ans = ans.replace(/%40/g, '@')
+    ans = ans.replace(/%5[bB]/g, '[')
+    ans = ans.replace(/%5[dD]/g, ']')
+    ans = ans.replace(/%5[eE]/g, '^')
+    ans = ans.replace(/%3[aA]/g, ':')
+    return ans
+
 def encode_query(query):
     if not query:
         return ''
@@ -15,7 +26,7 @@ def encode_query(query):
             val = query[k]
             if val is undefined or val is None:
                 continue
-            path += ('&' if has_query else '?') + encodeURIComponent(k) + '=' + encodeURIComponent(val.toString())
+            path += ('&' if has_query else '?') + encodeURIComponent(k) + '=' + encode_query_component(val.toString())
             has_query = True
     return path
 
diff --git a/src/pyj/book_list/boss.pyj b/src/pyj/book_list/boss.pyj
index b8c85433ac..400a4531f3 100644
--- a/src/pyj/book_list/boss.pyj
+++ b/src/pyj/book_list/boss.pyj
@@ -42,10 +42,16 @@ class Boss:
         if not data.mode or data.mode is 'book_list':
             if data.panel is not self.ui.current_panel:
                 self.ui.show_panel(data.panel, push_state=False)
-        elif data.mode is 'read_book':
-            self.current_mode = data.mode
-            self.apply_mode()
-            self.read_book(int(data.book_id), data.fmt)
+        if data.mode is 'read_book':
+            try:
+                book_id = int(data.book_id)
+            except Exception:
+                book_id = None
+            if book_id is None:
+                if data.panel is not self.ui.current_panel:
+                    self.ui.show_panel(data.panel, push_state=False)
+            else:
+                self.read_book(book_id, data.fmt)
         setTimeout(def():
             window.onpopstate = self.onpopstate.bind(self)
         , 0)  # We do this after event loop ticks over to avoid catching popstate events that some browsers send on page load
@@ -103,7 +109,6 @@ class Boss:
     def read_book(self, book_id, fmt, metadata):
         self.current_mode = 'read_book'
         self.apply_mode()
-        self.push_state(extra_query_data={'book_id':book_id, 'fmt':fmt})
         self.read_ui.load_book(book_id, fmt, metadata)
 
     def change_books(self, data):
@@ -131,6 +136,10 @@ class Boss:
                 query.search = sq
         else:
             query.mode = self.current_mode
+            if self.current_mode is 'read_book':
+                eqd = self.read_ui.url_data
+                for k in eqd:
+                    query[k] = eqd[k]
         if idata.library_id is not idata.default_library:
             query.library_id = idata.library_id
         set_current_query(query)
diff --git a/src/pyj/read_book/db.pyj b/src/pyj/read_book/db.pyj
index dc4d3b0059..66a8960e75 100644
--- a/src/pyj/read_book/db.pyj
+++ b/src/pyj/read_book/db.pyj
@@ -94,7 +94,7 @@ class DB:
                 'manifest': None,
                 'cover_width': None,
                 'cover_height': None,
-                'last_read_position': None,
+                'last_read_position': {},
             })
         )
 
diff --git a/src/pyj/read_book/iframe.pyj b/src/pyj/read_book/iframe.pyj
index 5dabb0dfe1..7670cd25ab 100644
--- a/src/pyj/read_book/iframe.pyj
+++ b/src/pyj/read_book/iframe.pyj
@@ -5,20 +5,29 @@ from __python__ import bound_methods, hash_literals
 import traceback
 from aes import GCM
 from gettext import install, gettext as _
+from read_book.cfi import at_current, scroll_to as scroll_to_cfi
 from read_book.globals import set_boss, set_current_spine_item, current_layout_mode, current_spine_item, set_layout_mode
 from read_book.mathjax import apply_mathjax
 from read_book.resources import finalize_resources, unserialize_html
-from read_book.flow_mode import flow_to_scroll_fraction, flow_onwheel, flow_onkeydown, layout as flow_layout
-from read_book.paged_mode import layout as paged_layout, scroll_to_fraction as paged_scroll_to_fraction, onwheel as paged_onwheel, onkeydown as paged_onkeydown, scroll_to_elem
+from read_book.flow_mode import (
+    flow_to_scroll_fraction, flow_onwheel, flow_onkeydown, layout as flow_layout
+)
+from read_book.paged_mode import (
+    layout as paged_layout, scroll_to_fraction as paged_scroll_to_fraction,
+    onwheel as paged_onwheel, onkeydown as paged_onkeydown, scroll_to_elem,
+    jump_to_cfi as paged_jump_to_cfi
+)
 from read_book.settings import apply_settings
 from utils import debounce
 
 FORCE_FLOW_MODE = False
 
-class Boss:
+class IframeBoss:
 
     def __init__(self):
         self.ready_sent = False
+        self.last_cfi = None
+        self.replace_history_on_next_cfi_update = True
         self.encrypted_communications = False
         window.addEventListener('message', self.handle_message, False)
         window.addEventListener('load', def():
@@ -83,13 +92,16 @@ class Boss:
             self.handle_wheel = flow_onwheel
             self.handle_keydown = flow_onkeydown
             self.to_scroll_fraction = flow_to_scroll_fraction
+            self.jump_to_cfi = scroll_to_cfi
         else:
             self.do_layout = paged_layout
             self.handle_wheel = paged_onwheel
             self.handle_keydown = paged_onkeydown
             self.to_scroll_fraction = paged_scroll_to_fraction
+            self.jump_to_cfi = paged_jump_to_cfi
         apply_settings(data.settings)
         set_current_spine_item({'name':data.name, 'is_first':index is 0, 'is_last':index is spine.length - 1, 'initial_position':data.initial_position})
+        self.last_cfi = None
         root_data, self.mathjax = finalize_resources(self.book, data.name, data.resource_data)
         unserialize_html(root_data, self.content_loaded)
 
@@ -109,13 +121,26 @@ class Boss:
         csi = current_spine_item()
         if csi.initial_position:
             ipos = csi.initial_position
+            self.replace_history_on_next_cfi_update = ipos.replace_history
             if ipos.type is 'frac':
                 self.to_scroll_fraction(ipos.frac)
             elif ipos.type is 'anchor':
                 self.scroll_to_anchor(ipos.anchor)
+            elif ipos.type is 'cfi':
+                self.jump_to_cfi(ipos.cfi)
+        self.update_cfi()
 
     def update_cfi(self):
-        pass  # TODO: Update CFI
+        cfi = at_current()
+        if cfi:
+            spine = self.book.manifest.spine
+            index = spine.indexOf(current_spine_item().name)
+            if index > -1:
+                cfi = 'epubcfi(/{}{})'.format(2*(index+1), cfi)
+                if cfi != self.last_cfi:
+                    self.last_cfi = cfi
+                    self.send_message('update_cfi', cfi=cfi, replace_history=self.replace_history_on_next_cfi_update)
+                    self.replace_history_on_next_cfi_update = True
 
     def onresize(self):
         if current_layout_mode() is not 'flow':
@@ -151,6 +176,7 @@ class Boss:
         if not name:
             name = current_spine_item().name
         if name is current_spine_item().name:
+            self.replace_history_on_next_cfi_update = False
             self.scroll_to_anchor(frag)
         else:
             self.send_message('scroll_to_anchor', name=name, frag=frag)
@@ -168,4 +194,4 @@ class Boss:
 def init():
     script = document.getElementById('bootstrap')
     script.parentNode.removeChild(script)  # free up some memory
-    Boss()
+    IframeBoss()
diff --git a/src/pyj/read_book/ui.pyj b/src/pyj/read_book/ui.pyj
index e7c992d290..a5120805f2 100644
--- a/src/pyj/read_book/ui.pyj
+++ b/src/pyj/read_book/ui.pyj
@@ -96,11 +96,20 @@ class ReadUI:
         div.lastChild.textContent = msg or ''
 
     def load_book(self, book_id, fmt, metadata):
+        self.base_url_data = {'book_id':book_id, 'fmt':fmt}
         if self.db is None:
             self.pending_load = [book_id, fmt, metadata]
             return
         self.start_load(book_id, fmt, metadata)
 
+    @property
+    def url_data(self):
+        ans = {'book_id':self.base_url_data.book_id, 'fmt': self.base_url_data.fmt}
+        bookpos = self.view.currently_showing.bookpos
+        if bookpos:
+            ans.bookpos = bookpos
+        return ans
+
     def db_initialized(self, db):
         self.db = db
         if self.pending_load is not None:
diff --git a/src/pyj/read_book/view.pyj b/src/pyj/read_book/view.pyj
index ccd0280c84..068bf3c41b 100644
--- a/src/pyj/read_book/view.pyj
+++ b/src/pyj/read_book/view.pyj
@@ -2,13 +2,14 @@
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 from __python__ import bound_methods, hash_literals
 
-from book_list.globals import get_session_data
+from book_list.globals import get_session_data, get_boss
 from dom import set_css
 from elementmaker import E
 from gettext import gettext as _
 from read_book.globals import messenger, iframe_id
 from read_book.resources import load_resources
 from read_book.overlay import Overlay
+from utils import parse_url_params, username_key
 
 LOADING_DOC = '''
 <!DOCTYPE html>
@@ -63,8 +64,9 @@ class View:
             'next_spine_item': self.on_next_spine_item,
             'goto_doc_boundary': self.goto_doc_boundary,
             'scroll_to_anchor': self.on_scroll_to_anchor,
+            'update_cfi': self.on_update_cfi,
         }
-        self.currently_showing = {'spine':0, 'cfi':None}
+        self.currently_showing = {}
 
     @property
     def iframe(self):
@@ -149,10 +151,28 @@ class View:
         self.book = book
         self.show_loading(book.metadata.title)
         self.ui.db.update_last_read_time(book)
-        # TODO: Check for last open position of book
-        self.show_name(book.manifest.spine[1])
+        pos = {'replace_history':True}
+        unkey = username_key(self.ui.interface_data.username)
+        name = book.manifest.spine[0]
+        cfi = None
+        q = parse_url_params()
+        if q.bookpos and q.bookpos.startswith('epubcfi(/'):
+            cfi = q.bookpos
+        elif book.last_read_position and book.last_read_position[unkey]:
+            cfi = book.last_read_position[unkey]
+        if cfi and cfi.startswith('epubcfi(/'):
+            cfi = cfi[len('epubcfi(/'):-1]
+            snum, rest = cfi.partition('/')[::2]
+            try:
+                snum = int(snum)
+            except Exception:
+                print('Invalid spine number in CFI:', snum)
+            if type(snum) == 'number':
+                name = book.manifest.spine[(int(snum) // 2) - 1] or name
+                pos.type, pos.cfi = 'cfi', '/' + rest
+        self.show_name(name, initial_position=pos)
 
-    def show_name(self, name, initial_position=None, cfi=None):
+    def show_name(self, name, initial_position=None):
         if self.currently_showing.loading:
             return
         sd = get_session_data()
@@ -162,16 +182,21 @@ class View:
             'read_mode': sd.get('read_mode'),
             'cols_per_screen': sd.get('cols_per_screen'),
         }
-        self.currently_showing = {'name':name, 'cfi':cfi, 'settings':settings, 'initial_position':initial_position, 'loading':True}
+        initial_position = initial_position or {'replace_history':False}
+        self.currently_showing = {'name':name, 'settings':settings, 'initial_position':initial_position, 'loading':True}
+        spine = self.book.manifest.spine
+        idx = spine.indexOf(name)
+        if idx > -1:
+            self.currently_showing.bookpos = 'epubcfi(/{})'.format(2 * (idx +1))
         self.set_margins(name is self.book.manifest.title_page_name)
         load_resources(self.ui.db, self.book, name, self.loaded_resources, self.show_spine_item)
 
     def goto_doc_boundary(self, data):
         name = self.book.manifest.spine[0 if data.start else self.book.manifest.spine.length - 1]
-        self.show_name(name, initial_position={'type':'frac', 'frac':0 if data.start else 1})
+        self.show_name(name, initial_position={'type':'frac', 'frac':0 if data.start else 1, 'replace_history':False})
 
     def on_scroll_to_anchor(self, data):
-        self.show_name(data.name, initial_position={'type':'anchor', 'anchor':data.frag})
+        self.show_name(data.name, initial_position={'type':'anchor', 'anchor':data.frag, 'replace_history':False})
 
     def on_next_spine_item(self, data):
         spine = self.book.manifest.spine
@@ -180,12 +205,21 @@ class View:
             if idx is 0:
                 return
             idx = min(spine.length - 1, max(idx - 1, 0))
-            self.show_name(spine[idx], initial_position={'type':'frac', 'frac':1})
+            self.show_name(spine[idx], initial_position={'type':'frac', 'frac':1, 'replace_history':True})
         else:
             if idx is spine.length - 1:
                 return
             idx = max(0, min(spine.length - 1, idx + 1))
-            self.show_name(spine[idx])
+            self.show_name(spine[idx], initial_position={'type':'frac', 'frac':0, 'replace_history':True})
+
+    def on_update_cfi(self, data):
+        self.currently_showing.bookpos = data.cfi
+        get_boss().push_state(replace=data.replace_history)
+        unkey = username_key(self.ui.interface_data.username)
+        if not self.book.last_read_position:
+            self.book.last_read_position = {}
+        self.book.last_read_position[unkey] = data.cfi
+        self.ui.db.update_last_read_time(self.book)
 
     def show_spine_item(self, resource_data):
         self.loaded_resources = resource_data
diff --git a/src/pyj/utils.pyj b/src/pyj/utils.pyj
index 5593321cdc..2e895796c7 100644
--- a/src/pyj/utils.pyj
+++ b/src/pyj/utils.pyj
@@ -128,6 +128,9 @@ def viewport_to_document(x, y, doc):
     y += wy
     return x, y
 
+def username_key(username):
+    return ('u' if username else 'n') + username
+
 if __name__ is '__main__':
     print(fmt_sidx(10), fmt_sidx(1.2))
     print(list(map(human_readable, [1, 1024.0, 1025, 1024*1024*2.3])))