Books about physics, string theory, space, and time

I'm working on a little fictional story/side-project that I'd like to start researching once I'm finished with school in May. It involves traveling between dimensions, and I'd like to have my concepts based on scientific theories.
Some of the books I've looked at on Amazon are The Elegant Universe and The Fabric of the Cosmos, both written by Brian Greene. I don't have a solid background in physics and I've never learned about this particular topic before, so I'm not really sure what to look for. I do know that I'm interested in theories about what keeps us in our present time/space; that sort of thing.
Any help or recommendations is appreciated
Some of the books I've looked at on Amazon are The Elegant Universe and The Fabric of the Cosmos, both written by Brian Greene. I don't have a solid background in physics and I've never learned about this particular topic before, so I'm not really sure what to look for. I do know that I'm interested in theories about what keeps us in our present time/space; that sort of thing.
Any help or recommendations is appreciated
