If I recall correctly, Nebula awards are typically voted on by the SF Writers of America Association, which means that by winning one it's generally a mark of recognition by your peers, a sign that you're admired by other writers in your field and worthy enough that a majority of them voted to give you an award (as opposed to the Hugo, which is generally voted on by the fans). In that sense, this is probably a book that will appeal more to writers than SF fans, if only because there is very little SF in the book at all. That doesn't mean it's not a well written, well constructed novel, it's just not very science-fictional. Those looking for a time travel type novel in the realm of Gregory Benford's "Timescape" or even HG Wells' "The Time Machine" will probably find themselves disappointed. Some time travelling apparently does occur but this isn't really a book where the focus is on fancy machinary and weird theories involving quantem physics. What we have here is the story of Joshua, a man who constantly "dreams" of a prehistoric past, a time when the forerunners of man walked the earth. He's tapped for a secret Air Force project in Africa where they have machines that will somehow harness his dreams and take him back to that time period, where he can report on what actually went on back then, things that the anthropologists can't figure out with just fossils and tools and whatnot. So Joshua goes back and winds up spending way more time there than he initially planned. Interspersed with the story of his adventures with proto-man are scenes from his early life, showing him growing up, interacting with a foster family and laying the seeds for what eventually would be his time travelling. The weird thing is, these interludes are far more interesting than the time travelling story, infusing the character with a lot more emotion and dimenesions than the other sequences do. The trip back starts out interesting, as Joshua runs into a small group of early man and integrates himself into their lives, and Bishop does a really good job speculating at what the society of early man might be like, their family groups and interactions with each other, as well as how they existed from day to day. Thing is, he gets that out of the way early and it just becomes aimless wandering, with Joshua's frequently flippant narration (he gives all the proto-men (and ladies) names, but I can't tell them apart, and tells them stories that are basically nonsense because they can't understand him anyway) substituting for anything resembling actual human interaction (because they can't talk to him and only have a limited understanding it's like he's rooming with a bunch of mimes) the prehistoric scenes start to suffer from a lack of direction, like Bishop found he liked the story of Joshua growing up a lot more and was just using the main story to kill time and space. Some scenes are pretty effective, especially the moments that deal with early mortality. But Bishop seems to be suggesting the whole thing is just a weird dream (does the gun ever run out of bullets?) and as such there are moments that don't make any sense at all (who the heck gets eaten?) and can only be attributed to dream logic. The big climax scene is basically solved by a "and then I decided we all could fly" solution and the aftermath of his time travelling is just . . . odd. Don't get the impression that I didn't like the book, I really did and Bishop gets credit for tackling the subject of time travel, both by using a different focus (prehistory) and for going about it in such an offbeat way. And by shuffling in the scenes of his youth, he adds a welcome depth to the character, to the point where I was looking more forward to the family scenes than anything else. That said, you can probably chalk this book up to "reach exceeds his grasp" sort of deal, where his ambition outstripped his ability. However, it's still well worth your time to track it down, especially if you're looking for something that isn't the tried and true and don't mind a little bit of the fantastic mixed in with your science.