diff --git a/src/calibre/gui2/__init__.py b/src/calibre/gui2/__init__.py
index 35cc249acb..b3e128af82 100644
--- a/src/calibre/gui2/__init__.py
+++ b/src/calibre/gui2/__init__.py
@@ -102,6 +102,7 @@ gprefs.defaults['cb_fullscreen'] = False
 gprefs.defaults['worker_max_time'] = 0
 gprefs.defaults['show_files_after_save'] = True
 gprefs.defaults['auto_add_path'] = None
+gprefs.defaults['auto_add_check_for_duplicates'] = False
 # }}}
 
 NONE = QVariant() #: Null value to return from the data function of item models
diff --git a/src/calibre/gui2/add.py b/src/calibre/gui2/add.py
index 7cdac3b845..972ea57cb9 100644
--- a/src/calibre/gui2/add.py
+++ b/src/calibre/gui2/add.py
@@ -382,7 +382,8 @@ class Adder(QObject): # {{{
         if not duplicates:
             return self.duplicates_processed()
         self.pd.hide()
-        files = [x[0].title for x in duplicates]
+        files = [_('%s by %s')%(x[0].title, x[0].format_field('authors')[1])
+                for x in duplicates]
         if question_dialog(self._parent, _('Duplicates found!'),
                         _('Books with the same title as the following already '
                         'exist in the database. Add them anyway?'),
diff --git a/src/calibre/gui2/auto_add.py b/src/calibre/gui2/auto_add.py
index 0319a67210..6860f386d6 100644
--- a/src/calibre/gui2/auto_add.py
+++ b/src/calibre/gui2/auto_add.py
@@ -15,6 +15,7 @@ from PyQt4.Qt import (QFileSystemWatcher, QObject, Qt, pyqtSignal, QTimer)
 from calibre import prints
 from calibre.ptempfile import PersistentTemporaryDirectory
 from calibre.ebooks import BOOK_EXTENSIONS
+from calibre.gui2 import question_dialog, gprefs
 
 class Worker(Thread):
 
@@ -159,12 +160,11 @@ class AutoAdder(QObject):
         count = 0
 
         needs_rescan = False
+        duplicates = []
 
         for fname, tdir in data.iteritems():
             paths = [os.path.join(self.worker.path, fname)]
             sz = os.path.join(tdir, 'size.txt')
-            if not os.access(sz, os.R_OK):
-                continue
             try:
                 with open(sz, 'rb') as f:
                     sz = int(f.read())
@@ -173,6 +173,11 @@ class AutoAdder(QObject):
                             ' we tried to read metadata')
             except:
                 needs_rescan = True
+                try:
+                    self.worker.staging.remove(fname)
+                except KeyError:
+                    pass
+
                 continue
 
             mi = os.path.join(tdir, 'metadata.opf')
@@ -180,18 +185,45 @@ class AutoAdder(QObject):
                 continue
             mi = [OPF(open(mi, 'rb'), tdir,
                     populate_spine=False).to_book_metadata()]
-            m.add_books(paths, [os.path.splitext(fname)[1][1:].upper()], mi,
-                    add_duplicates=True)
+            dups, num = m.add_books(paths,
+                    [os.path.splitext(fname)[1][1:].upper()], mi,
+                    add_duplicates=not gprefs['auto_add_check_for_duplicates'])
+            if dups:
+                path = dups[0][0]
+                with open(os.path.join(tdir, 'dup_cache.'+dups[1][0].lower()),
+                        'wb') as dest, open(path, 'rb') as src:
+                    shutil.copyfileobj(src, dest)
+                    dups[0][0] = dest.name
+                duplicates.append(dups)
+
             try:
                 os.remove(paths[0])
-                try:
-                    self.worker.staging.remove(fname)
-                except KeyError:
-                    pass
+                self.worker.staging.remove(fname)
+            except:
+                pass
+            count += num
+
+        if duplicates:
+            paths, formats, metadata = [], [], []
+            for p, f, mis in duplicates:
+                paths.extend(p)
+                formats.extend(f)
+                metadata.extend(mis)
+            files = [_('%s by %s')%(mi.title, mi.format_field('authors')[1])
+                    for mi in metadata]
+            if question_dialog(self.parent(), _('Duplicates found!'),
+                        _('Books with the same title as the following already '
+                        'exist in the database. Add them anyway?'),
+                        '\n'.join(files)):
+             dups, num = m.add_books(paths, formats, metadata,
+                     add_duplicates=True)
+             count += num
+
+        for tdir in data.itervalues():
+            try:
                 shutil.rmtree(tdir)
             except:
                 pass
-            count += 1
 
         if count > 0:
             m.books_added(count)
diff --git a/src/calibre/gui2/preferences/adding.py b/src/calibre/gui2/preferences/adding.py
index 0cd0aa4657..d35df2a183 100644
--- a/src/calibre/gui2/preferences/adding.py
+++ b/src/calibre/gui2/preferences/adding.py
@@ -32,6 +32,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('automerge', gprefs, choices=choices)
         r('new_book_tags', prefs, setting=CommaSeparatedList)
         r('auto_add_path', gprefs, restart_required=True)
+        r('auto_add_check_for_duplicates', gprefs)
 
         self.filename_pattern = FilenamePattern(self)
         self.metadata_box.layout().insertWidget(0, self.filename_pattern)
diff --git a/src/calibre/gui2/preferences/adding.ui b/src/calibre/gui2/preferences/adding.ui
index 9b7401447c..73d305631d 100644
--- a/src/calibre/gui2/preferences/adding.ui
+++ b/src/calibre/gui2/preferences/adding.ui
@@ -193,6 +193,19 @@ Author matching is exact.</string>
          </property>
         </widget>
        </item>
+       <item>
+        <widget class="QCheckBox" name="opt_auto_add_check_for_duplicates">
+         <property name="toolTip">
+          <string>If set, this option will causes calibre to check if a file
+ being auto-added is already in the calibre library.
+ If it is, a meesage will pop up asking you whether
+ you want to add it anyway.</string>
+         </property>
+         <property name="text">
+          <string>Check for &amp;duplicates when auto-adding files</string>
+         </property>
+        </widget>
+       </item>
        <item>
         <spacer name="verticalSpacer_2">
          <property name="orientation">