People have their faves. I personally like ABC, A Basic Course. That is what I primarily learned from. This was before I took formal classes. At my college the course is taught using Bravo and Signing Naturally. These are preferred because they have video’s with them that show proper sign production. I personally do not care for them. That may be due to learning from ABC so I might be partial. A website that I love but others do not is aslpro.com I would say try your library before buying one of the suggestions people post. Find our suggestions and see which seems to be the best for you, most easy to understand. Once you have made your decision then buy the books. This way you haven’t spent money on something you wish you hadn’t later.