Animorphs Book 20: The Discovery by K. A. Applegate

The Discovery is part 1 of 3 of the David sequence. I like this approach to telling a longer story by connecting three books more tightly than the rest of the continuity. The Animorphs have to deal with more exposure while protecting world leaders.

Knowing what's to come, by comparison this is pretty light. The rest of this sequence is going to be very dark and deal with some very heavy stuff, but for now there's a new element and he doesn't work well with Marco.