The Hidden Alphabet by Laura Vaccaro Seeger
First off, I am a huge fan of books that allow the children to interact so when I got the book and saw it had “peek a boo” pages I was excited to read it. I love how clever the author used the flaps. Each page is black with a “window” of something labeled on the page when you lift the flap you see that she used the actual letter to create the item. Here is letter B for an example.
This book would probably be better for 3 and up seeing that some of the words used are advanced.