For me I like Robert B. Cialdini books Influence: The Psychology of Persuasion & Yes! 50 Scientifically Proven Ways to Be Persuasive. Anything to add more persuasion in a subconscious way does it for me
If you like books specifically for getting in the groove of writing, one you might like is "The Writer's Workout: 366 Tips, Tasks, and Techniques". On the psychology and persuasion side of things, check out a book title "Brainfluence". Both are excellent reads and books you'll always learn something from when you come back to them.
Those are all good, some of my favorites are: Scientific Advertising-Claude Hopkins Ultimate sales letter-Dan Kennedy Adweek Copywriting Handbook- Joe Sugarman
ca$hvertising is a good reference , it tells lots of modern technique of advertising. i love the part on attracking people with images, something that not much copywriting books would discuss
Try reading "Triggers" by Joe Sugarman. This book has to do with copywriters understanding their readers and writing accordingly. A most interesting book.
I love reading new books particuarly those that inspire me. i am going to check out these books. Thank-you for sharing these favorites that help you to get your creative juices flowing.