Used science-fiction books seem hard to find in Cuba. I get the impression that those who are lucky enough to own them tend to hang on to them, and so it's a rare book stall that has any genre fiction for sale. I was able to purchase a couple of volumes, but most of the books I obtained in Havana were gifts from the writers and editors I visited.
Below (with minimal information, I'm afraid) is a small sampling of Cuban science-fiction book covers.
 Cuentos Cubanos de Cinecia Ficción 1983 The first anthology of Cuban science fiction Juan Carlos Reloba Santana, editor |
 Los Papeles de Valencia el Mudo 1983 Oscar Hurtado a collection by one of Cuba's most influential SF writers |  ¿Donde Esta Mi Habana? 1985 F. Mond |
 Una Leyenda del Futuro 1985 Augustin De Rojas |  El Elegido 1988 Julián Pérez |
 Nova de Cuarzo 1999 Vladimir Hernández Pacín A collection of cyberpunk stories |
 Los Pecios y los Náufragos 1999 José Miguel Sánchez (writing as Yoss) |
 El Duida 2000 Gina Picart |
 Sol Negro: Crónicas de Sotreun 2001 Michel Encinosa Fú |
 Niños de Neón 2001 Michel Encinosa Fú |
After spending some time with these volumes—and a good Spanish-English dictionary—I hope that I'll be able to report further on the flavor of these works.