There was a different letter printed in the end of the last book, one that didn't explain her reasoning anywhere near as well.

...Awww. I possess the entire Animorphs series, but was lucky enough to get into it while it was already ended/practically over.

*hugs* I'd prefer a non-cliffhanger ending, personally. I can deal with Rachel being dead, I can deal with Tobias being unhappy, I can deal with Ax leaving. What I can't deal with is the idea of everything not being ended, and them never getting any peace.