Back when I did the exam, Bob Tait was perfect study prep. Know the law, and/or know where to find it in the regs, but be aware, the exam is all about attempting to trip you up. Unless something's changed recently, IREX is an exercise in RTFQ a number of times over and identifying where it's trying to trip you up - as most of the harder questions do.
IREX study gives you a good base of book knowledge to get your CIR issued, which in turn gives you the bare skills necessary to not kill yourself under the IFR. The actual learning then begins.
There are other publications which are better sources of overall IFR theory... But are inferior at simply preparing you for the exam. Once the rating is issued... Absorb every bit of knowledge you can. For now, get yourself over the exam line.
Ebby, I see nothing wrong with his attitude, unlike yours.
Good luck with it all.