Well, the 4th grade textbook may be down, but here's a link to all of them. Some of them even have previews!

I've only skimmed through a couple of them so far. The "high school" books seem boring, as it's mostly just dumbed-down science (instead of hilariously wrong). The 5th grade text's preview is just about rocks and also very boring, except for the part on page 9 where it says when you study geology, you're also studying geometry because rocks have, like, different shapes and stuff.

I'll probably go through the rest at some point this weekend, and I'll point out any more gems I find.