Sweet was born in Highland Park, New Jersey. He graduated from Syracuse University in 1956 with a degree in fine arts. He also produced art for trading cards and calendars. He was famous for providing the covers of the fantasy epic saga The Wheel of Time, save for that of the final book, which postdated Sweet's death. He was also the illustrator for the well-known Xanth series by Piers Anthony, the covers of the Pelbar Cycle by Paul O. Williams, the Saga of Recluce series by L. E. Modesitt, Jr. and the Runelords series by David Farland as well as the original cover artist for Stephen R. Donaldson's series The Chronicles of Thomas Covenant the Unbeliever.
