I wish there had been more multi-part stories in the Animorphs books. There are the Megamorphs but those don't have much impact on the main series. I don't have a lot to say other than these books remain some of the best.
ETA: Except for the computer stuff in this book! Every time I read it and the kids think they can stop the email from being sent by just unplugging the internet I die inside. Are they secretly Boomer parents who think that deleting the IE icon from the desktop deletes the internet from the computer?