Signing Everyday Phrases by Mickey Flodin
If you just want a basic dictionary with illustrations, these two books offer a good resource for vocabulary.
Talking With Your Hands, Listening With Your Eyes: A Complete Photographic Guide to American Sign Language by Gabriel Grayson
This next book was made by a man who is an interpreter for the deaf in the New York City Circuit courts. Although hearing himself, both of Grayson's parents were deaf. His book contains photographs of different signers that, with the exception of him, are all deaf. Each person is introduced at the beginning of the book, with a brief but interesting biography.
Also included throughout the book are little vignettes of trivia about famous deaf people, the origin of sign language and other interesting tidbits of information about sign language.
All three books and the online course are worth buying and having more than one book is necessary because none of them have complete vocabularies.