I've read the inner game of tennis. Great book! make it your bible.
Also read 'The best tennis of your life' by Jeff Greenwald. A few consider it the modern inner game of tennis and I agree. I read it after the inner game of tennis and a good chunk was review and dumbed down. A much easier read imo.
Definitely read 'Winning Ugly' by Brad Gilbert after mastering the two books aforementioned.