Interworld

This is a young adult novel coauthored by Neil Gaiman and Michael Reaves.

Admittedly, it's been a while since I read it, so I can't say anything very specific.

Probably the biggest thing fans of Neil Gaiman will notice is a fairly large departure from Gaiman's traditional style, even more so than in Good Omens, which he coauthored with Terry Pratchett. And, though I hate to say it about anything Gaiman has touched, this is a fairly average book.

I guess if you liked Ender's Game (by Orson Scott Card) then Interworld might be right up your alley.