This is the Office of Tourism for Brocéliande located at the end of the main road in Paimpont. There is a small shop inside with lots of Merlin, magical, and fairy themed items. Prices are a bit high and I didn't see any books in English.
Once you enter, to the right is La Porte des Secrets (http://www.yelp.com/biz/la-porte-des-secrets-broc%C3%A9liande-paimpont) where you can go on a tour about Merlin! read more