4 stars because it is one of the best MCAT Verbal Prep books out there (other one is Princeton Review Hyperlearning). Not 5 stars because... well... it's the MCAT.
I don't have much to compare to but according to forums and my friends, EK seems to mimic the actual MCAT verbal section the best...its hard to get the particular MCAT style of questions well but Ek is close. However, the passages on the actual MCAT are longer than the ones in EK.
a bit out of date -- 9 passages/85 minutes/60 questions rather than the standard 7 passages/70 minutes/40 questions now used on CBT. somewhat demoralizing how low your score gets, but from the time that i started to when i finished, using aamc tests as a standard, improved by 5 questions (unfortunately, with how steep the scale is that only resulted in 1 point...)