Yes. Arthur C Clarke and Robert Heinlein. Clarke's Ringworld series and Heinlein's Lazarus Long books. Oh, and Harry Harrison wrote the Stainless Steel Rat series, it was great fun. He also wrote a serious alternative history of the American Civil War...
I just loved Arthur C Clarke's "Tales of the White Heart". A collection of short stories.
Heard about C Clarke and Heinlein's series I think but had no idea about Harry Harrison.
Thanks a lot, will check them out!