Lord Valentine's Castle

I'm not sure whether Lord Valentine's Castle is properly fantasy or sci-fi. It's somewhat akin to Wolfe's New Sun/Long Sun/Short Sun series, taking place in a post-technological world, where some super-science still abounds, but the culture has become more medieval in a lot of ways. Valentine has lost his memory, and treks across the strange, alien world he grew up on. It is clever in many ways, albeit a bit linear -- it's good, but packs few surprises, not much deep philosophy, nor radical inventions. I enjoyed it quite a bit, but left feeling the whole thing needed one more ingredient. I'm not sure what that extra thing could have been, in what is generally an excellent read, but that is the only reason I mark it a 4, rather than a 5.