Kudos---a Greek word that is singular, not plural, my friends---to Joe Haldeman, who wins my Best Novel Ending Award for The Accidental Time Machine. It's a brand new award, which is why you haven't heard about it. Very low key ceremony, no need to rent a tux.
Obviously, I can't tell you the book's conclusion. But it's the rare twist ending that is clever yet somehow inevitable. Once you read it, you think, "Well, yeah. I suppose that had to happen." Yet it's not what you've been expecting for the last third of the book. Let's call it the "duh" twist. Skilled!