I used all the EK books, including all the 1001-questions and verbal 101 books. Basically all the concepts are covered, so it is enough to prepare you for the test. However, it depends on your abilities because different books will explain certain concepts in different ways. For me, physics was a weakness, so I also got the Nova book and went through that, and even though they cover the same stuff, I liked the way Nova explained certain topics and EK on other topics. So the combination of the two definitely helped.
The 1001 questions books are good for conceptual practice, it really exposes your weakness and rams it into your head until you get it. They are not good for MCAT-style practice. For test-prep I used the AAMC (obviously) practices and Gold Standard practices.
Search the forums, there is a lot of information about strengths and weakness of different books.