Just curious about what areas chess.com users study most, especially those with a decent chess library.

What percentage of your chess books would you estimate fall into each of the following categories: General, opening, midgame, endgame, game collections, problems, and biography (feel free to add any classes I have overlooked). Also, if you had to select one book as the most effective at improving your game, what would it be?

My own library is about 30% endgame, 25% midgame, 20% opening, 10% game collections, 5% general, 5% problems, and 5% biography. The most helpful for me has been Reuben Fine's Basic Chess Endings.

I'm surprised and disappointed to see zero responses to this...

I am a medical student.So reading chess books is difficult for me.However when i get time I read a chapter of this and a chapter of that...random..This is helpful and fun and needs less committment.

maybe you would get more of a response in the chess books and equipment section. 

Not looking at my collection now.  But probably a few more opening books than middlegame.  Slightly less of endgame and middlegame.  Probably book I got the most improvement out of was winning chess middlegames and or forcing chess moves.  Before those books I was missing some basic mating combinations and had a simplistic view of the isolated pawns-  ie they are just weak. 

A third book that I got a lot out of was aagards excelling at technical chess.  GOt a lot out of which pieces to exchange etc. 

A lot have chess books.It is just that the topic is not interesting.Most consider it meaningless to post a list of their books.Me too , I have more than 200 , I need 2 days typing.