Worked very well for me. Information was concise, but also clear and easy to follow. I would only recommend this for people with a good background in science though, since it makes assumptions sometimes that you know basic First Year University concepts. I also purchased the 1001 questions set for Physics, Chem, and Org Chem (highly recommended) and the 101 passages in Verbal reasoning (highly highly recommended), I heard the bio one was not as good though so I didn't buy that.
Examkrackers was the only resource I used, and although there was definitely some errors and spelling mistakes, it got me the mark I wanted (and then some), so I have to review them pretty well. I would have given 5 stars but there were a lot of spelling and grammatical errors that would sometimes bother me.