Xenocide, from the ender series. Enders game was good. Speaker was OK I guess. Ender was a whiny bitch the entire time but the descolada mystery was interesting. Now that's solved and he's still a whiny bitch and then he just solves basically every single problem with his super ai that can do magical space/time bullshit. The worst deus ex machina I have ever laid eyes on. I physically threw the book across the room at one point. I hate leaving books unfinished, so I slogged through the rest at like 5 pages per sitting, rolling my eyes out of my head the whole time.
I have to rank Children of the Mind as one of the just plain weirdest books I've ever read. Just when I thought it couldn't get weirder, Orson Scott Card manages to throw something else at you. After I finished Children of the Mind, I decided at that point I was going to move onto some other book series.
I'll still recommend Ender's Game as that's a classic, but I wouldn't bother with the sequels.
Anything with Ender after the first book is terrible. But the series that sticks with the happenings on earth after Enders Game is pretty good. I especially like the book that has Bean from a child through battle school.