An Un-Calibrated Centrifuge

What did I just read? This is the mess that The Familiar avoided becoming. While that one was weird in a way that worked this one is just weird.

Why waste Rachel's last book on the return of David. Was anyone really dying to see him again?

More under the cut (with spoilers).

I see two outcomes to bringing David back. 1. Redemption (didn't happen) or 2. Death (likely happened, but why the cliffhanger?) Seriously why not just write the scene? I mean, this book gets pretty dark in places and the series overall deals with some heavy stuff so why shy away from this?

Also, why all the concern that the Yeerks will find David now? He's always known the Animorphs were a bunch of kids. It's a moot point anyway because there's that little fact of the free Hork-Bajir made into a Controller in the last book also knew the Animorphs's secret so the Yeerks know too but everyone is just ignoring that for some reason (most likely because the ghost writer forgot to put it in the book).