Those do sounds like good books to look into.

We had a fun tubby moment with dd2.5 the other day: We have foam letters in the tub for her and she picked up the 'F' and said, "Look, P for foot!" and stuck it on her foot. I laughed and said "That's an F and foot does start with F! And it looks a lot like a P", and we talked about how they look alike and different. I figured it was a coincidence that she grabbed the right letter...then later she had the 'Z' turned sideways in her hand and said 'nnn' for Nemo!
Ok, maybe less coincidence than I thought.