In general, the best American books I did find useful about 11 years ago, were those of usmle BOOKS PARt I, II AND III by Appleton & Lange, editors, (besides of a good collection of gannongs physiology, and harpers biochemistry, etc)
They are cheaper, more understandable, and directed to the exams,,,,,
USMLE part III reqiores a special course, because it does NOT follow the pattern of answering of the parts I and II....
Besides the Kaplan courses are quite useful (the Compass company I used, closed down years ago)....and there are trainig courses with books and personal orientation in the UK,,,,
best of luck....