I also found it bland; it became repetitive and dull. Problem, exposition of solution, repeat. The character interaction, by the nature of the plot, was pretty minimal and almost all the problems were technical - there was very little inter-character conflict or character development. At the end of the novel, everyone was pretty much the same as they were at the beginning. The journey was entirely physical, and the dangers were personal.
I am befuddled that you say the characters were superbly fleshed out; I found them rather two-dimensional, and some of them clearly existed only because there needed to be more people hanging around.
I completely agree – very unrealistic characters (maybe that's why there was no character development). Also there was a lot of exposition about how extraordinarily 'funny' the main character was and I didn't get that at all, it felt very heavy handed with the jokes. Also, the bit about cannibalism made no sense whatsoever.
I am befuddled that you say the characters were superbly fleshed out; I found them rather two-dimensional, and some of them clearly existed only because there needed to be more people hanging around.