Is it worth purchasing or should I just stick with specific books geared for a particular subject? If it’s any good should I get it off of Amazon or College Board itself? Amazon seems to have mixed reviews as of 2017 with some saying it’s outdated.
There are plenty of PDF for the the official study guide online so check those our first. If I were you I get a specific book for your subject.
College board has new released tests for Bio, Physics and Chemistry with the curves and scoring. Amazon sells them as well as the college board itself. The questions are very current. I highly recommend them as to figure out the style of the questions that will be in the actual test and to gauge your ability in the end of studying. The other prep books are good to study the materials but their tests are a bit off.
I borrowed one from the school library because I just needed one test from it.