EGGS 1-2-3: WHO WILL THE BABIES BE? is my new favorite find in this category. This lift-the-flap book is by Janet Halfmann.
This book is not only a nonfiction book--it has great, poetic language and it is also a counting book! Each two-page spread gives readers a little question about eggs in the illustration. For example "Four eggs, of sky blue, in a nest of grass and mud on a branch in a backyard. Who will the babies be?" When you lift the flap, you read, "4 robin chicks, with beaks open wide, begging for juicy worms.
The book goes from 1-10 with a fun last page of more counting. I like this book because it weaves in just the right amount of information about the eggs and the babies that hatch from them. I love it for young readers and I also love it as a mentor for writing--a great format for nonfiction writers with information shared using great language.