This is an original cover illustration for the alternate history fantasy novel by Poul Anderson, published by Ballantine Books, in paperback, 1975 (I show the cover as reference).  Nominated for multiple awards, Sweet's artwork captures the essence of the fun Anderson had in consuring this parallel world, where the plot is shaped both by "A Midsummer Night's Dream" and "The Tempest"  A great vintage painting, done in acrylic on gypsum board, 24" x 16"  and signed.