Ambitious, certainly, and having finished it in less than a week, it doesn't seem like a 770-some-page book. The structure, I think was something of a problem, particularly the break from the first section/timeframe to the second. All of the sudden the chracters we care about aren't even referenced (one of them doesn't return until the very end, and then only...briefly). The colony-world was well-fleshed out. It was particularly refreshing that the society of the colony was neither naively harmonic nor oppresively discordant. They certainly have their problems--the same problems you get whenever you throw humans together--but that's not necessarily the point of the book. It's about the ending and saving of the world. It's an adventure. And not a bad one.