At some point, I made a list of 'Favorite SF&F that someone who likes many of the same books as me might not have heard of'.
- Dimension of Miracles, by Robert Sheckley
- Blue and Gold, by K. J. Parker
- Invisible Cities, by Italo Calvino
- The Collapsium, by Wil McCarthy
- A Madness of Angels, by Kate Griffin
- Radiance, by Cathrynne Valente
(Honorary mention: Every Heart A Doorway, by Seanan McGuire. While it seems like hardly anybody I know has read it, a book that won the Hugo and Nebula can'r really be considered 'lesser-known SF&F')