I almost forgot these 2; Leyendas españolas de todos los tiempos and Leyendas de Euskal Herria.Every name is a book in Lectulandia Just copy paste the names on the white rectangle of the upper right. Also search for Gustavo Adolfo Bécquer, the last romantic of spain, and maybe from the world. Almost every one of his leyendas is an idea for an Aquelarre campaign, and he was a very good writer. Tales of the Alhambra by Washington Irving is the only book of this you could find in English. Sorry if this looks extensive, but I really like the myths and legends of spain.
If you want to know more, search for a tv show called Cuarto Milenio and a couple of radio Shows, milenio 3,Noche de Misterios, La Rosa De los Vientos,Turno de Noche and Zona Negra. Search in youtube something like, cuarto milenio pueblos abandonados, la santa compaña, edad media, ruta de los pueblos malditos Also, I’m gonna post the Aquelarre apocrifo for you. This is basically a relic from the internet of the 90s and beginnings of the 2000s. Is the old email list of the game, the original fan club of the game, who used to post a lot of stuff about everything in medieval Spain. Take a look to chapter 6, it has a lot of recommendations, to music for the campaigns, essays relevant to the game, movies, works of fiction, like Don Quijote or La Vida Es Sueño, and a few other medieval games you could like. The 1 chapter is where the legends are, the one about Pedro I of Portugal look like a Shakesperian drama or like the theater of el Siglo De Oro. I hope this will be useful to you