diff --git a/src/calibre/gui2/actions/add.py b/src/calibre/gui2/actions/add.py
index e18f5fe77c..4071ad1468 100644
--- a/src/calibre/gui2/actions/add.py
+++ b/src/calibre/gui2/actions/add.py
@@ -14,6 +14,7 @@ from calibre import as_unicode
 from calibre.gui2 import (error_dialog, choose_files, choose_dir,
         warning_dialog, info_dialog)
 from calibre.gui2.dialogs.add_empty_book import AddEmptyBookDialog
+from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.dialogs.progress import ProgressDialog
 from calibre.gui2.widgets import IMAGE_EXTENSIONS
 from calibre.ebooks import BOOK_EXTENSIONS
@@ -119,7 +120,6 @@ class AddAction(InterfaceAction):
         if current_idx.isValid():
             view.model().current_changed(current_idx, current_idx)
 
-
     def add_recursive(self, single):
         root = choose_dir(self.gui, 'recursive book import root dir dialog',
                           'Select root folder')
@@ -205,7 +205,6 @@ class AddAction(InterfaceAction):
                         'authors']))
                 return
 
-
             mi = MetaInformation(None)
             mi.isbn = x['isbn']
             if self.isbn_add_tags:
@@ -227,7 +226,8 @@ class AddAction(InterfaceAction):
             return
         db = self.gui.library_view.model().db
         current_idx = self.gui.library_view.currentIndex()
-        if not current_idx.isValid(): return
+        if not current_idx.isValid():
+            return
         cid = db.id(current_idx.row())
         from calibre.gui2.dnd import DownloadDialog
         d = DownloadDialog(url, fname, self.gui)
@@ -235,7 +235,7 @@ class AddAction(InterfaceAction):
         if d.err is None:
             self.files_dropped_on_book(None, [d.fpath], cid=cid)
 
-    def files_dropped_on_book(self, event, paths, cid=None):
+    def files_dropped_on_book(self, event, paths, cid=None, do_confirm=True):
         accept = False
         if self.gui.current_view() is not self.gui.library_view:
             return
@@ -243,8 +243,10 @@ class AddAction(InterfaceAction):
         cover_changed = False
         current_idx = self.gui.library_view.currentIndex()
         if cid is None:
-            if not current_idx.isValid(): return
+            if not current_idx.isValid():
+                return
             cid = db.id(current_idx.row()) if cid is None else cid
+        formats = []
         for path in paths:
             ext = os.path.splitext(path)[1].lower()
             if ext:
@@ -257,10 +259,18 @@ class AddAction(InterfaceAction):
                     db.set_cover(cid, pmap)
                     cover_changed = True
             elif ext in BOOK_EXTENSIONS:
-                db.add_format_with_hooks(cid, ext, path, index_is_id=True)
+                formats.append((ext, path))
                 accept = True
         if accept and event is not None:
             event.accept()
+        if do_confirm and formats:
+            if not confirm(
+                _('You have dropped some files onto the book <b>%s</b>. This will'
+                  ' add or replace the files for this book. Do you want to proceed?') % db.title(cid, index_is_id=True),
+                'confirm_drop_on_book', parent=self.gui):
+                formats = []
+        for ext, path in formats:
+            db.add_format_with_hooks(cid, ext, path, index_is_id=True)
         if current_idx.isValid():
             self.gui.library_view.model().current_changed(current_idx, current_idx)
         if cover_changed:
@@ -277,10 +287,9 @@ class AddAction(InterfaceAction):
             to_device = allow_device and self.gui.stack.currentIndex() != 0
             self._add_books(books, to_device)
             if to_device:
-                self.gui.status_bar.show_message(\
+                self.gui.status_bar.show_message(
                         _('Uploading books to device.'), 2000)
 
-
     def add_filesystem_book(self, paths, allow_device=True):
         self._add_filesystem_book(paths, allow_device=allow_device)
 
@@ -453,3 +462,4 @@ class AddAction(InterfaceAction):
             self._adder.add(ok_paths)
 
 
+