Here’s a book on a subject I’d like to know more about – and oh look, it’s free to read online! Courtesy of the Library of Iberian Resources Online (LIBRO).
Paganism and Pagan Survivals in Spain up to the Fall of the Visigothic Kingdom, by Stephen McKenna
The upside – this is a subject that we don’t see much published on, in English.
The downside – it’s a Catholic publication from the 1930s, which means (as can be seen in the very first sentence of the preface) that it is full of offensive language about and attitudes towards the pagans under discussion… so take that for what it’s worth.