In Search of the Multiverse, has the exact same premise.
Because of that, a lot of what I could say about this book I've already said. If you don't feel like reading the other review, here's a short summary:
"This is a book about what is "sci" and what is "fi" about multiverses. It's got lotsa types and no equations. Certain fancy people agree with the author."
So, what makes The Hidden Reality different from In Search of the Multiverse? Well, In Search of the Multiverse focuses a lot more on visualizations and analogies of the universes described. The Hidden Reality presents things in a slightly more scientific fashion.
Another difference is that The Hidden Reality has grouped it's multiverses into nine categories, all of which are easily found in the contents, that are summarized by Wikipedia. This gives the book a more focused, purposeful narrative (if you can call it that), whereas In Search of the Multiverse feels more like a ramble about the topic (an organized ramble, but a ramble).
You should get whichever book sounds more appealing. Or, if neither sound appealing, why not try Masterminds? It's super good. And, hey, if you want to get both, go ahead. They don't say all of the same things, so they compliment each other well.
P.S.: I, personally, liked The Hidden Reality better. Not only is it delivered in a way that I like more, but it is also written by Brian Green, who wrote and made movies of Fabric of the Cosmos and The Elegant Universe, the first of which I've seen and loved.
P.P.S. I think this is a record for the most links in one post that I've made so far. If not, well now it is.