They are completely different books. EK 101 is a book full of 11 FLs that you can take for extra practice. I don't believe they updated the EK 101 book for the new MCAT. However, I'm still using it in my prep. On the other hand, EK reasoning skills gives you more information & strategy tactics for the CARS section. It also includes both a math & research skills section that (in my opinion) is advantageous for this new MCAT.
