I think that the Bond, GL (old), CGP are all test materials. One should focus on core concepts that are never going to change. I mean fractions are just fractions and verbal is just knowledge of words. Therefore, all books are relevant.
Format (CEM or whatever) is largely cosmetic, it would still test the same stuff. Yes, you may have to fine-tune the approach slightly (cloze, speed for CEM etc) but fundamentals would remain same. Therefore, spend all the energy on understanding fundamentals at this stage.
FYI, we did Bexley CEM that was introduced last year and used the same approach (and my ds cracked full 280). I could be wrong but it worked for us.