After 15 hours my instructor thought I was ready for the test after one more lesson. I was unconvinced. The "one more lesson" showed that I was correct
Book 5, Confuser and RANT. Nobody has ever suggested to me that ground school beyond self study and the instructor's long briefings is necessary. The real exam questions seemed to be easier than the Confuser, containing far fewer silly trick questions for example. If you already have an adequate flight simulator you won't need RANT as well. I reckon RANT saved a couple of hours flying, ie paid for itself several times over - I can make much more sense of the holds and approaches if I've already "flown" them on RANT using today's wind forecast before I get into the aircraft.
All these points have been discussed at greater length in recent threads, either here or on Flyer.