I have EK's 1001 questions for both organic and chemistry. i think they are a nice way to get practice solving problems as well as getting concepts straight since they ask about 10 questions in different ways for each concept.
no, there's no passages to explain concepts, but what it lacks in rote information, it makes up for in variance of question formats, imho...
don't get the biology one, and don't get the reading comp. or math one, those are definitely MCAT specific.