I used EK, which i found to be adequate. But, I also used the Flowers book, which i found myself turning towards more and more as my studying went on. In retrospect, I wish i had used that book more than i did. It is very easy to understand, it covers basically everything you're gonna need, and it is not as dry as some of the other books like Kaplan comprehensive (book should be used as a sleep aid, i can't recommend this book at all).
EK offers good prep books (especially physics). But, I found the quality of their writing to be spotty at best. Some sentences i would read and have no idea what they were trying to say. Other times, i was amazed at their analogies and how easily they cleared up confusing topics with just a few sentences on the topic.
Regarding Flowers, yes, Blitz is correct the questions are far easier than you're gonna find on the actual mcat, so don't depend on them to prep you or you'll be in for a rude surprise. There are also some errors, but not that many, and if you're studying from multi sources you'll catch them no problem.
Overall, i highly recommend Flowers and would suggest using it in tandem with another prep company, i found EK to be good, but the choice is yours
