A 2007 Science Fiction novel by Neil Gaiman and Michael Reaves about Joey, a boy who finds out the hard way that he is a "Walker", meaning he can jump between the many alternate universes. The good news: no Evil Twin. The bad news: not one, but two Evil Empires trying to take over the multiverse. Long story short, Joey ends up joining an inter-universal army whose mission is to keep neutral realities safe in the war of Magic Versus Science.The sequel was released April 23, 2013, and was name Interworld: The Silver Dream. It revolves around Joey Harker once again, however he and his team meet a mysterious girl, who calls herself Acacia Jones. After going on a mission to save a new Walker, and retrieve data from the clutches of Binary the plot thickens.
Butterfly of Doom: Only major changes cause new realities to form, but major changes can be caused by seemingly minor actions. As described in the book, if a butterfly can eventually cause a hurricane, then stepping on the butterfly before it can flap its wings might be enough to split reality.
Chekhov's Skill: The winged Joey can use her wings to slow herself and someone she is carrying down while falling, even if she's on a world where she can't fly.
The Chosen One: It turns out that all of the Walkers are the Joeys from different realities, even the ones that are older or women.
Cyborg: One of the Walkers comes from a world where everyone is cyberized at birth.
Depth Deception: Due to existing beyond the usual 4 dimensions, nobody can be certain just how large MDLFs are. For example, Hue is mentioned to either be the size of a housecat from 2 feet away, to the size of a skyscraper from several miles away, to the size of the state of Vermont from several thousand miles away.
No Sense of Direction: Joey has gotten lost in his own house. Turns out that it's because his brain isn't wired for three-dimensional travel.
Not So Different: Hex and Binary have the same goals, abilities, and treat humans like animals. For example, one Hex wants to boil down the Walkers' bodies until only their soul are left; the other wants to slowly drain out his energy over the same period while keeping him in cold storage.
Painting the Medium: When Joey has his memories erased, one of the pages goes completely black.
Sesquipedalian Loquaciousness: One of Joey's teammates speaks this way because "what's the point of having words if you're not going to use them". Even the cyborg with several implanted dictionaries has trouble keeping up at times.
Took a Level in Badass: Joey, after months of training. In addition to being physically strong, he's been taught such advanced science and math that he goes from being a remedial student to one of the best. Since this is after the Mind Wipe, he has no idea why he can suddenly do so well.
Winged Humanoid: One of Joey's teammates has angel-like wings. Since they function by magic, they tend not to work well on the more science-y worlds.
Year Outside, Hour Inside: When Joey returns to his world after months of training and having his memory erased, only about 36 hours have passed.
You Can't Go Home Again: Joey can never return to his home dimension, lest HEX or The Binary track him there and attempt to take over, possibly killing his family in the process.