[BetterRed]

@holyfeld - on windows I get this if I double click a TPZ book I add to calibre

calibre, version 2.3.0
ERROR: Unhandled exception: <b>WindowsError</b>:[Error 1155] No application is associated with the specified file for this operation: u'E:\\CalibreData\\_Test\\Whoever\\Whatever (198)\\Whatever - Whoever.tpz'

calibre 2.3 [64bit]  isfrozen: True is64bit: True
Windows-7-6.1.7601-SP1 Windows ('64bit', 'WindowsPE')
('Windows', '7', '6.1.7601')
Python 2.7.8
Windows: ('7', '6.1.7601', 'SP1', 'Multiprocessor Free')
Successfully initialized third party plugins: FictionDB && Count Pages && Beam Ebooks && Generate Cover && Open With && Quality Check && User Category && Favourites Menu && Quick Preferences && Manage Sony x50 Reader Book List && Reading List && Walk Search History && Barnes & Noble && Goodreads && Find Duplicates && Import List && Resize Cover && EpubSplit && View Manager && Extract ISBN && Modify ePub
Traceback (most recent call last):
  File "site-packages\calibre\gui2\actions\view.py", line 225, in view_triggered
  File "site-packages\calibre\gui2\actions\view.py", line 301, in _view_books
  File "site-packages\calibre\gui2\actions\view.py", line 260, in _view_calibre_books
  File "site-packages\calibre\gui2\actions\view.py", line 101, in view_format_by_id
  File "site-packages\calibre\gui2\actions\view.py", line 150, in _view_file
  File "site-packages\calibre\gui2\actions\view.py", line 140, in _launch_viewer
  File "site-packages\calibre\gui2\__init__.py", line 1120, in open_local_file
WindowsError: [Error 1155] No application is associated with the specified file for this operation: u'E:\\CalibreData\\_Test\\Whoever\\Whatever (198)\\Whatever - Whoever.tpz'

What do you have in Preferences->Tweaks-># Control behavior of the book list

And does your MAC have file association for TPZ, I don't have anything - hence the above msg makes sense.

Very odd that double click should want to add the book.

BR