it was more than just ringworld though that I like about Niven
its the whole KNown space thing, slavers, protectors, kzinn etc etc. The consistancy in the "science" was, for its time, fantastic.
and if you were evre into wargaiming then the barsoom project etc were very good. Though not too sure if you were not into it that they would be so good.
Niven gave me one of my favourite sayings
"think of it as evolution in action"
the mote in gods eye is aslso a classic.
I like larry niven as you may have guessed