I haven't got in yet...so maybe someone who has would have a more inside view of the relevancy of each book, but I really like Kenneth Isserson's book on getting into med school. It talks about the traditional path into md school, but also covers foreign med school, osteopathic school, minorities, women, older, etc applicants. It has a lot of tables comparing tution, MCAT, GPA stats of various schools, which obviously change from year to year (at least tuition does) but provides good relative cost comparison. He goes through the interview process, personal essays, and includes one very interesting chapter on how you should select a med school based on your needs and wants. If I was only getting one book I would get this one.
I also liked "Essays that will get you into Medical school" for essay advice, the MSAR (obviously) for 'official' info, and 'The Insiders guide to medical schools'. The last of these is a collection of essays by students at each med school saying what they feel about their school. It's not that informative as most of them are the usual "my school is great, great city, caring faculty, etc, etc" but in some essays it's more revealing what they don't say about their school than what they do.