Just Finished "Downward to the Earth" by Robert Silverberg - What of His Books Should I Read Next?

I demolished Downward to the Earth today. It's one of those books that is going to stick with me for a long time. This is the first Silverberg book I've read and I really loved his writing style and prose.

I also have Dying Inside on the docket. Which other of his books should I be checking out?

Also, if there are other new-wave authors who you think are similar to Silverberg I'll happily take those recs as well.