TEN+TEN is very fun and nostalgic! The first 9 songs each represents one of their 9 previous album, borrowing pieces and phrases from them, but turning their essence into a new song. That's followed by the entirely new "TEN". Then for the second disc/last 10 songs, it's all covers and remixes featuring a bunch of different artists (including Chip Tanaka!)
(putting the song for Family Genesis here because that's the YMCK album I listen to the most C: )