You guys baffle me. Ironically, I just read this book yesterday. Finished it in a bit over 2 hrs. Great read. Especially the opening. If there's one thing KA does really well, its writing the opening sequences. Anyone remember MM3 book opening? Very disturbing but interesting.
MM4 was an important story. It showed Jake's reaching his breaking point, even though there was plenty more to come. It represented Cassie as an anomaly, an explanation as to why she was so well grounded, so stable, so moralistically cool, and a bit mystic, and in a sense, what made her give the Yeerks to morphing cube.
It showed that Rachel would have indeed dated Marco. If it happened, it would have happened. Truth don't lie.
Tobias def would have ended up with the Sharing, making a huge mistake on his part, only to realize that hey, he could have endured his rough teenage years. That's loads better than losing your freedom to an alien slug.
If it weren't for Cassie though, and for the already happened timeline, the Animorphs would have fallen to the influences of the undercover Yeerks. Eventually. But then again, Ax would've screwed things up big time.
And in the end, all was not lost. The Ellimist stated that although the Animorphs did all die in that alternate timeline, they still were able to take out a lot of the Yeerks by blasting the Pool Ship. And millions of humans would have died, but the VICtory would eventually come. The Yeerks would not have won.
The importance of the story is that the Animorphs HAD to become the heroes they were to save millions from dying. To stall. To save humanity from total destruction, and most importantly, to save themselves. As much as I hated the final book ending #54, it was still way happier than the ending we saw in MM4