The book starts out with a terrific premise - the idea of using an "inversion drive" to travel through de Sitter Space to travel extraordinary distances. Extra-galactic travel would be possible, for instance. One third of the way through the book is a Klingon ambush that I wish would have been more developed, but was nevertheless very exciting.Midway through, however, the story begins to rely heavily on fantasy sequences that are happening in the minds of the crew. A little bit of this is okay, but by the end, the story is dominated by it. That was very disappointing, and didn't have much of a science-fiction feel to it. For that reason I can't recommend this book.