This has to be one of the smartest, most creative works of fiction I've ever read. Add to that funny, poignant, deeply philosophical. And for all its frenetic energy, none of it is superfluous.
I honestly don't understand the criticisms of the work. They seem to be either from people who don't understand it, missed its point completely, or were looking for something to criticize. Racist? Please, this is the last book you'd want to play the race card on. Excessive metaphor? It's the style of the novel, all quite apropos. One chapter began with, what I thought, was a rather contrived metaphor, and then Robbins turned it around by the end of the chapter and gave it brilliant significance.
Read this book. With all the people who gave it mediocre reviews, I can't promise you'll like it, but it certainly won't be a waste of precious reading time.