Ender In Exile (Ender, #1.5)
I always enjoy books set in the Ender-Universe, but this book can hardly be called a novel. It has no conflict, nothing to resolve, no build-up, no stakes. Card introduces plot-lines at the beginning that completely fizzle out near the middle, only to be replaced by plot-lines that are extremely complex at the end of the novel. It's just kind of a mess. Like indulgent, canon fan-fiction.
Not to mention that it just feels small in comparison to the high-stakes intelligence and spirituality of Ender's Game and Speaker for the Dead. All the meat Card could have gotten out of the prequel concept was mostly squandered, and as a result the book mostly feels like a series of snapshots rather than an organic story.
With all that being said, however, Orson Scott Card (and Ender in particular) happens to be my particular kind of crack, and I still very much enjoyed it.