Trying to remember the name of a children's sci-fi book from the 90s. [Solved]

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I want to say the main character was a girl, but no matter the gender they were in their early teens.

The core of the book (which isn't explicitly revealed until it's been going on a while) is a machine that somehow alters time and space and is slowly going out of control. Because of this the whole book takes place out of sequence and repeats as the machine changes the place and order of major events. The only other strong memory Ive got is of some aliens (maybe not aliens, I just know they were from somewhere else) who used obsidian tunnels or something to travel around.

I can't be the only person who read this book, but I have no idea how to even begin googling for it.

Also, I'm assuming it was written in the 90s because that's when I read it and I think it was fairly new. I could be wrong.

tynic

That sounds a bit like Hexwood, but I'm not sure.

edit: Hexwood is, without a doubt, Diana Wynne Jones' most complex book. The scenes happen in the wrong order, every character (including the Bannus itself) suffers from a case of mistaken identity at some point in the book, and both ordinary Earth businessmen and men from outer space are deluded into believing they are knights.

does this sound right?

Iruka

Time, space and aliens with a girl protagonist makes me think of A Wrinkle in Time, But I cannot remember enough of the book to say for sure.

Edit: I dont remember scenes being particularly out of order, though, so i may be way off.

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My first thought was A Wrinkle in Time as well, but the descriptions I've read don't seem to fit. I do remember reading it, as well.

Hexwood is probably it. I must have passed over it on googled lists because of the name.

Just googled the cover. It's definitely Hexwood. I will be hunting down a copy soon and I hope it's as entertaining as I remember.

see317

Wrinkle in Time also fails the "From the 90s" bit.

Still, it's a good read. The sequels, not so much.