Here is a link to what books the AP people say meet their curriculum. http://www.collegeboard.com/html/apcourseaudit/courses/biology_textbook_list.html
If you are self studying I suggest getting a Campbell text book and a review guide to go with it. The Campbell books are good in terms of completely covering the material and a review guide would be more of a diagnostic tool since you aren’t actually taking the class. I suggest a non-Barons guide. The Barons are great if you know the material at an upper 4 or 5 level but they are much too critical for lower score levels.