(Mild) spoiler warning!
I thought the characters in the novel took Platonism (they call the world of forms the "Hylaean Theoric World") more seriously than it deserves. It turns out later in the book that there are parallel universes, which they interpret as being multiple Hylaean Theoric Worlds.
But of course that didn't really disturb my enjoyment of the book. Regularly when I was reading it I found something I thought about posting here. It made me laugh out loud some, but the tone is more serious than his other stuff. The story takes place on another planet with humanoid inhabitants; there are many parallels to the world we know, but there are very few jokes that would only seem funny to someone from Earth. (A pair of characters who like to have intense conversations with one another, ignoring other people, are nicknamed "the creature with two backs".)
The Onion AV Club just did an interview with Stephenson.