Hyperspace is a good book by Michio Kaku I read some time back. It talks about parallel universe, quantum leap, wormhole, tele-portation, time wraps and 10th dimension.
Although these are not proven, his theory is that, there are infinite number of parallel universes around us and travelling to other universe is possible through wormhole, which needs enormous amount of energy.
One of the interesting thing mentioned in the book is, different universes are not of same size. some universe might be as small as size of a atom. and other can be trillions time bigger. However we will never notice how big those universe are if we travel to them because everything is shrink down or expanded in proportion. For example, if everything in earth is shrink down by half, we will never notice our height has been reduced to half because everything around us will be reduced to half as well, including the scale to measure.