I don't think that there's a 100% accurate book. It's a matter of how it's used and where you're using it.
I've read some ASL books where there were signs that I didn't even recognize, but I already knew the sign for it myself... from other sources.
So, who is to say which sign is accurate. There's no formal organization that approves these things.
I've seen some ASL teachers not approve some books that are approved by other ASL teachers. That's why I hesitate when it comes to helping ASL students with their ASL because I am sometimes shot down for doing it wrong due to being "incorrect" as stated by their ASL teachers. :roll: