It is a truly great time travel novel, and has always been in my top 5 list of ANY novels I've read (his wonderful Pirate book, On Stranger Tides is also squeezed into that short list!). But, these things are SO subjective. Especially with Powers, who isn't "horror" at all (although there are certainly horrific moments in his books- and a lot of us folks who love horror seem to like him), but more of an alternate history, arcane secrets, adventure fiction kind of writer. The bottom line is it is pretty universally praised as a "great" book- the question is do you like that sort of fiction? If the "flap copy" description interests you at all- you'll more than likely dig it because it's extremely well done. If it sounds weird, or dull to you- you might not.
I will say that in this market where virtually EVERYTHING comes out in an expensive "Limited Edition"- this is the rare book that actually deserves it. But, I come at these things differently from most of the people on this site who mostly seem to covet the rarity of these items- I am only interested in the beauty of the object (the more copies the better, imo), and the story inside, of course. I am overjoyed that one of the best reads ever is being produced in what appears to be one of the best looking books ever done.
Hey, if you don't like- you can probably at least make your money back on it someday!
Ron