Originally I was really annoyed with the trend of teaching babies sign language. Like parents need another thing to feel inadequate about. But for whatever reason I picked up this book at my public library, and learned about what started this craze. Originally teaching babies sign language was not about giving parents another way to compete with their gifted tots, but a tool to help parents understand the needs of their very young children who hadn't mastered spoken language yet. Basically, the researchers involved in the study Baby Signs are based on learned that older infants and young toddlers want to communicate, but lack the control of their vocal chords to do so with spoken language. Using simple signs (some based on American Sign Language, some simpler versions related to what the objects do or look like) babies can express basic needs, such as hunger, thirst, or a dirty diaper, and identify some of the things commonly in their world like dogs, cats, and other animals. The argument is that this is a parenting tool to aid communication and alleviate a lot of the fussiness common during the "Terrible Twos" which many parents will tell you often starts well before age two.
As a book, this is awfully repetitive and a little infomercial-ish, but the opening chapters discussing the reasons for developing baby signs and the research study done on it's effectiveness totally sold me and made me confident that I could take the signs included at the end of the book and immediately start using them with my son.
There are actually quite a few printable resources on the Baby Signs website, so parents might consider going there instead of paying for a book where the only part you really use is the signing dictionary.
My own son's on the young side of being ready for signs, but he loves dogs and loves when I do the sign for dog (sticking your tongue out and panting) because he also loves sticking his tongue out. I don't think he's quite figured out the connection yet, but he's watching and learning and I'm confident that in a month or two, he'll start signing back to me.