diff --git a/src/calibre/devices/usbms/driver.py b/src/calibre/devices/usbms/driver.py
index 0d3779a309..3d65dfba35 100644
--- a/src/calibre/devices/usbms/driver.py
+++ b/src/calibre/devices/usbms/driver.py
@@ -10,6 +10,7 @@ driver. It is intended to be subclassed with the relevant parts implemented
 for a particular device.
 '''
 
+import posixpath
 import os
 import re
 import json
@@ -61,7 +62,7 @@ class USBMS(CLI, Device):
         # make a dict cache of paths so the lookup in the loop below is faster.
         bl_cache = {}
         for idx,b in enumerate(bl):
-            bl_cache[b.path] = idx
+            bl_cache[b.lpath] = idx
         self.count_found_in_bl = 0
 
         def update_booklist(filename, path, prefix):
@@ -71,9 +72,9 @@ class USBMS(CLI, Device):
                     lpath = os.path.join(path, filename).partition(prefix)[2]
                     if lpath.startswith(os.sep):
                         lpath = lpath[len(os.sep):]
-                    p = os.path.join(prefix, lpath)
-                    if p in bl_cache:
-                        item, changed = self.__class__.update_metadata_item(bl[bl_cache[p]])
+                    idx = bl_cache.get(lpath.replace('\\', '/'), None)
+                    if idx is not None:
+                        item, changed = self.__class__.update_metadata_item(bl[idx])
                         self.count_found_in_bl += 1
                     else:
                         item = self.__class__.book_from_path(prefix, lpath)
@@ -109,6 +110,7 @@ class USBMS(CLI, Device):
         # find on the device. If need_sync is True then there were either items
         # on the device that were not in bl or some of the items were changed.
         if self.count_found_in_bl != len(bl) or need_sync:
+            print 'resync'
             if oncard == 'cardb':
                 self.sync_booklists((None, None, metadata))
             elif oncard == 'carda':
@@ -173,7 +175,7 @@ class USBMS(CLI, Device):
             lpath = path.partition(prefix)[2]
             if lpath.startswith(os.sep):
                 lpath = lpath[len(os.sep):]
-
+            lpath = lpath.replace('\\', '/')
             book = Book(prefix, lpath, other=info)
 
             if book not in booklists[blist]:
diff --git a/src/calibre/gui2/device.py b/src/calibre/gui2/device.py
index f890515aa5..9511e1c752 100644
--- a/src/calibre/gui2/device.py
+++ b/src/calibre/gui2/device.py
@@ -1043,29 +1043,37 @@ class DeviceGUI(object):
 
     def set_books_in_library(self, booklists, reset=False):
         if reset:
-            # First build a self.book_in_library_cache of the library, so the search isn't On**2
-            self.book_in_library_cache = {}
-            for id, title in self.library_view.model().db.all_titles():
-                title = re.sub('(?u)\W|[_]', '', title.lower())
-                if title not in self.book_in_library_cache:
-                    self.book_in_library_cache[title] = {'authors':set(), 'db_ids':set(), 'uuids':set()}
-                au = self.library_view.model().db.authors(id, index_is_id=True)
-                authors = au.lower() if au else ''
+            # First build a cache of the library, so the search isn't On**2
+            self.db_book_title_cache = {}
+            self.db_book_uuid_cache = set()
+            for idx in range(self.library_view.model().db.count()):
+                mi = self.library_view.model().db.get_metadata(idx, index_is_id=False)
+                title = re.sub('(?u)\W|[_]', '', mi.title.lower())
+                if title not in self.db_book_title_cache:
+                    self.db_book_title_cache[title] = {'authors':set(), 'db_ids':set()}
+                authors = authors_to_string(mi.authors).lower() if mi.authors else ''
                 authors = re.sub('(?u)\W|[_]', '', authors)
-                self.book_in_library_cache[title]['authors'].add(authors)
-                self.book_in_library_cache[title]['db_ids'].add(id)
-                self.book_in_library_cache[title]['uuids'].add(self.library_view.model().db.uuid(id, index_is_id=True))
+                self.db_book_title_cache[title]['authors'].add(authors)
+                self.db_book_title_cache[title]['db_ids'].add(id)
+                self.db_book_uuid_cache.add(mi.uuid)
 
         # Now iterate through all the books on the device, setting the in_library field
+        # Fastest and most accurate key is the uuid. Second is the application_id, which
+        # is really the db key, but as this can accidentally match across libraries we
+        # also verify the title. The db_id exists on Sony devices. Fallback is title
+        # and author match
         for booklist in booklists:
             for book in booklist:
+                if getattr(book, 'uuid', None) in self.db_book_uuid_cache:
+                    self.book_in_library = True
+                    continue
+
                 book_title = book.title.lower() if book.title else ''
                 book_title = re.sub('(?u)\W|[_]', '', book_title)
                 book.in_library = False
-                d = self.book_in_library_cache.get(book_title, None)
+                d = self.db_book_title_cache.get(book_title, None)
                 if d is not None:
-                    if getattr(book, 'uuid', None) in d['uuids'] or \
-                            getattr(book, 'application_id', None) in d['db_ids']:
+                    if getattr(book, 'application_id', None) in d['db_ids']:
                         book.in_library = True
                         continue
                     if book.db_id in d['db_ids']: