The Calle de Claudio Moyano has been likened to the area full of book stalls that lines the Seine in Paris with its many trestle tables and wooden sheds bursting with books. The street leads up in a diagonal line at the south west corner of Retiro park and is just a little way along from Atocha metro station so it's easy to find.
The books are mostly secondhand and in Spanish but many stalls have a small foreign languages section with English, French, German and Italian titles. There's a good mix of modern and older titles and there are definitely some gems to be found if you do a bit of digging; I even came across a Spanish copy of Richmal Crompton's Just William along with plenty of other children's books. Amongst piles of Spanish classics I found translations of the Lord of the Rings, Twilight and Bridget Jones' Diary. There are boxes and racks of film posters, old post cards, maps and newspapers though I would definitely say that this is a place for people that mainly have books in mind.
It was a Sunday when I visited so some of the stalls weren't open; I'll certainly be visiting again to pick up my next Spanish book to read. The prices are pretty reasonable with an average book being around 3-5 euros, though there are plenty to be found at less than that, and stall holders are often happy to offer you a deal if there are a few that you can't bear to be parted with. I'm so happy I've found this place; it's become one of my favourite spots in Madrid and the fact that it's right next to Retiro park doesn't hurt. I've also been hearing about a potential Book Fair that might take place in the city in the summer time so am definitely looking forward to that!