I enjoyed reading and seeing the subtle differences between the Voyagers -- although in the last half we hear and see and learn little of the planet they are trying to save. The climax occurs very late in the book, and the story ties up a little too tightly, but the characterizations make up for it.
An enjoyable read -- the titles under the chapters are also unique and inviting, helping readers keep track of which universe and which "shift." Definitely more reliable than the Stardate system. ;)
I like sci-fi that also adds some philosophical discussion or ideas to the story, and that is what this did. The idea of multiple dimensions and Janeway over a com-line with various versions of herself from those dimensions is quite intriguing to me. While this is by no means a new idea, I enjoyed the manner in which the story was told.
Since my reading this (in 2001) I've read numerous other Trek Books and this is still my favorite.