Okay, I wanted to address something KitsuneMarie said but it was said under a spoiler tag so I'm just going to have to bury my whole comment:
[spoiler]"I know the final conflict involving Ax is probably troubling for a lot of readers, too, but it provides a tenuous reason for the Animorphs guys to regroup (which is the best we could expect after all the understandable resentment between Tobias and Jake), and it confirms that their love for their friends is stronger than their anger towards each other."
The thing is, I really like that, EXCEPT that Cassie didn't go. I would have been a LOT more okay with the whole entire book if only that one thing had been changed. If the whole group was able to put aside their anger because "their love for their friends is stronger," then the whole group should have gone, for Ax's sake. I mean, I think I had a lot of issues with that book, but that was something that I thought was maybe one of my bigger issues...[/spoiler]