Help me find a book (you know, if you want)

[ChippedShoulder]

I realise that this is at least a semi-common thread so first of all I'd like to say that this can of course be used for anybody else to look for books that time (and they) forgot.

I need help finding a book I remember reading six or seven years ago. I can't remember the name (obviously) or author but the cover was deep red with a green jewel type thing on the hardcover edition. It was about an organisation that involved teenagers flitting between either time or worlds (can't remember which, think it was the latter) and selling technology by barter. Things go awry when a small group of them (one of whom I believe was called Theresa or something similar) end up (I think) stuck in one of these worlds. I can give spoilers via pm to anybody who thinks they may know from this what I'm talking about.

Thanks guys.

 

[Wintermute_v1legacy]

Doesn't sound like anything I've read before, but you can always try your luck here:

http://www.goodreads.com/group/show/185-what-s-the-name-of-that-book

 

[Evil Smurf]

Check out the "His Dark Materials" series by Philip Pullman. It's a favourite of mine.