Sequels are always interesting creatures. This is one of the class that is like the original, although not quite as tightly developed, not quite as fully connected within itself and very clearly a middle book, a book to keep the readers involved and interested and up to date with the developments in the world. It is, in short, the second book in a trilogy. But the story remains interesting and the combination of writers means that both the science and the fiction is deeply enjoyable. The idea behind the story, of infinite numbers of iterating worlds, remains engaging and one of the most fun versions of "what if humanity could do X?" that I have read in a long time.
If you enjoyed the first one, this one is definitely worth picking up.