I recommend Master Class I and II and Mastering the Mental Game by Saul Kirsch. Saul pretty well covers all IPSC related shooting positions and more. Mastering Mental Game is good too, lots of talk but god talk.
Tapes, books are additions, good additions, but best is a live training with trainers who can show and explain how to and when to and so on.
If someone is serious about improving in IPSC shooting Levels I, II and occasionally III is not enough. Best training is done at home learning draws (especially strong and weak or surrender), learning mags changing, calling targets, and transitions. All we need is pistol, mags, practice ammo with no primers and powder, CED7000 timer for pars and you ready to go.
Good book for practicing in the basement is Steven Anderson: " Refinement and Repetitions..."
Good Luck