the obvious one for physical game is game changer by mark baker. the best mental book i've read is focused for bowling by dean hinitz. both have helped me out a tremendous amount since the summertime. haven't seen any dvd's but i'm interested in that quiet mind one that just came out

Norm Duke's Competitive bowling DVD is great,it contains a lot of good drills and other useful info.

I haven't watched it yet but there's a DVD out by Storm called "The Quiet Mind". Supposed to help you quiet your conscience and get your mind out of the way to let the body do it's job for cleaner, easier repeated shot making.

Would like to check this one out personally. Now that I have my approach in full swing with the hinge style that helps me make shots almost effortlessly, pair this up with the quiet mind and things could get really dangerous on the lanes.

For something a little different, I would suggest "The Inner Game of Tennis: The Classic Guide to the Mental Side of Peak Performance" by W. Timothy Gallwey.  Great book on the mental side of competition and how competing isn't only against an opponent, but also your own mind.  Plus, it will give you a break from all of the bowling based books.  Nothing wrong with bowling books, but once I got a couple, a new perspective was refreshing.