Once I got past the first 100 pages (which I didn't find terribly compelling) the story took hold and I had trouble putting the book down -- all 495 pages of it. While it blends history and science fiction, it is done extremely well. The writing is competent and the characters alive and believable.
It would be a wonderful beach read as the weather warms. I recommend it highly. It also helps to refresh your memory by first reading "Rime of the Ancient Mariner", which is a pleasure in any event.