Moral or not, legal or not, but it’s pretty easy to download if it’s complicated to buy in your country)
Probably the best beginner’s book for Latin I’m aware of. Audio included. Really a must have for Latin learners!
Here’s the “official” online list of distributors for Lingua latina per se illustrata: http://www.lingua-latina.dk/ . <www.amazon.fr> has many of the books listed for sale, too.
The author of the Lingua Latina books sadly died early last year.
I’m using it right now in LingQ and it’s working quite brilliantly. My suggestion is to not even bother with the dictionaries on here but instead to use wiktionary (English) and just paste the words straight into it (with macrons) and get good definitions there.
The www.lingua-latina.dk website is not operating any more 
eugrus, That’s too bad.
I haven’t found a similar site, looking around this evening. In the U.S. at least publishing or distribution of his books seems still to be carried on by Focus Press. I’ve also seen a Spanish-language site that offers all of the materials. (I’ll be glad to post links if you like.)