Project Gutenberg offers free books in Spanish. As of 2015, the website offers more than 100 free Spanish-language books in a variety of electronic formats.
Find Project Gutenberg's selection of Spanish-language books by visiting its homepage at Gutenberg.org, then clicking on Browse Catalog near the top. From there, click on the Spanish link to find a directory of Spanish-language books listed alphabetically by author. Most books published on Project Gutenberg's website are available in HTML format for browser reading as well as a variety of e-reader compatible formats. Project Gutenberg is an organization dedicated to publishing free, public-domain books electronically, so its website also offers e-books in a variety of other languages.