I'm trying to remember a YA Sci-Fi book, probably from the 2000s, about a boy who is randomly attacked by what looks like wizards and robots. He is then saved by someone who appears to be an older version of himself and taken to another dimension which is almost identical to his own.

He learns that these worlds are created from choices; one choice creates one world, and the other choice creates another. Eventually, they fall into a spectrum with magic being at one extreme end and science at the other. Both extremes are trying to take over the other Earths in between. The only one who can travel between the worlds is that world's version of himself.

There's the older him, a girl him, a werewolf him, and an old man him. Basically, all the versions of him are gathering to try to stop this conquest. The magic and sci-fi empires hate each other. At one point, it's revealed that each empire is able to travel between worlds by kidnapping hundreds of versions of this one guy and using them like a battery.

The protagonist we follow tries to leave at one point and has his memory wiped, but then remembers everything because of a floating ball 4th dimension sidekick character whom he befriended while walking through the 4th dimension between worlds.

I think there are more books in the series, but I just read the one.

  • Hi, welcome to SF&F. Can you pin down the year you read it any more specifically? Do you recall the cover art?
    – DavidW
    Commented Jun 24 at 3:29
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1 Answer 1


InterWorld 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 4th dimension sidekick is a Multi Dimensional Life Form named Hue.

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.

Another bit from the linked tvtropes page:

It turns out that all of the Walkers are the Joeys from different realities, even the ones that are older or women.

And about the ships used by the bad guys:

The engines used by Hex and Binary are fueled by the souls of captured Walkers.

  • Duplicate of scifi.stackexchange.com/questions/282839/… and others.
    – Shawn
    Commented Jun 24 at 6:52
  • Interesting that the size of the MDLFs are all roughly equivalentish. A small object up close, a medium sized object at a distance, a very large object at a great distance...
    – FreeMan
    Commented Jun 26 at 14:58

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