I am surprised to see quite a few negative reviews here on our favorite books - it looks like many people don't like the "baby signs" series of little books just because these are not based on ASL. IMHO, this is akin to criticizing a French text book because it doesn't teach Spanish. If it's ASL that you want to teach your baby, just pick books on that subject and leave these alone.My baby and I are casual signers and I have not read the author's Baby Signs book for parents, but just from my own experience as a mommy, I can think of several good reasons to use "made-up" signs instead of ASL:- If you're not already fluent in ASL, you won't need to go search in a dictionary or on the Internet every time you want to sign something new to your baby, which would mean losing good opportunities for introducing new signs.- Some ASL signs are more complicated and while not exactly difficult, can be pretty unnatural for babies to do when they're just starting to learn how to control their hands.- If baby comes up with a gesture himself that has meaning you understand, you can go along with him instead of "correcting" him.And here are some additional "pros" on this series of adorable board books:- Having the object pictured side-by-side with a baby demonstrating the sign is brilliant. The pictures of the object are often selected to include a version that babies would be more familiar with, like a stuffed animal. The pictures of the happy babies are great for your baby to identify himself with and to want to imitate.- The "review" page at the end of each book shows pictures of all the objects without the signs, so you can point to each one, say the word, and let your baby try doing the sign.- Did I already say adorable? Not only I love the pictures, my baby does, too! He not only learns the signs, but also learns to say the words with these books. "Baby" (or more like "baaa-beeeee") was one of my baby's first words, and he says it when he asks to read these books (which is all the time).And these provide such a fun and loving way for babies to learn to express themselves and communicate with their parents! Ultimately, that's what I want to do with my baby, not stressing ourselves out trying to do ASL correctly. Baby and I highly recommend all 4 "baby signs" board books in this series.