Prep book instead of Text Book?

So, I’m going to take 3 Social Science APs this year. And what both the Internet and people I know keep saying is that it’s really important to keep up on the reading. I’ve purchased AP prep books and they seem to have lots of information put together in a very concise matter ( think REA Crash course). So, why should I read 30 pages of text book when I can read 15 in a prep book? I understand that it could be a problem for in-class assignments but if I know we’ll just be discussing the material, then me knowing the general idea should do.
Just thinking aloud, but has someone done this before?</p>

<p>Ive got a good example for this. My junior year i took the APUSH class and read A HUGE textbook filled with all kinds of material. However, i neglected studying for the exam in favor of other AP exams and i got a 3.</p>

<p>My senior year i decided to take APUSH again, so i bought a review book and simply read that + REA crash course.</p>

<p>When it came down to the essays (and even some of the multiple choice), i actually remembered some obscure relevant details from the textbook that i used last year. I later went into my review book afterwards and didnt find that info.</p>

<p>Bottom line, Review/Prep books are exactly what they are: Prep and Review for the exam. Textbooks are the main course.</p>