Re-reading just two seems like it would be disappointing or at least less than the effect you're looking for.....I'd either re-read them all and get to the new one when done, regardless of when that is, or just read the new one and re-read everything down the road......but you gots to do what makes ASHLEY happiest, since you're Ashley and all.
Crap on a stick I'm excited for the next book. And I already miss the TV series, it really did the book justice.