I've bought two Princeton Review (SAT II physics/Chemistry) to get prepare. The results is just fine when I do the practice tests. But is the result trustworthy? I've found little error in the books (little, but little is more than none).
By the way, this is part of a chemistry problem which I think its answer is wrong:
Q: Consider the reaction: 2NOCl(g) <--> 2NO(g)+Cl2(g)
Does a decrease in the volume of the reaction vessel serve to decrease the concentration of Cl2?
The answer in the book is yes. Well, of course after a decrease in the volume the equilibrium shift to the left. But you increase the concentration of Cl2 when you decrease the volume, don't you? And after some calculation I believe that the concentration is increased...