When Leo was little he was obsessed with eggs. We still read a lot of egg books. Lately we've been enjoying this one, Guess What Is Growing Inside This Egg by Mia Posada (Millbrook, 2007). It's an especially good choice for reading aloud to kids of different ages (like mine, who are 7 and 3). Milly still likes to guess what's in each egg, on the basis of a close-up like the one on the front cover and a little riddle like this one (from the back cover):

Under this feathered belly, it's cozy and warm.
The egg is safe from the icy Antarctic storm.

"It's a penguin!" she tells me excitedly, every single time. When we turn the page, Leo can hear or practice reading aloud a short paragraph about penguins (or alligators, ducklings, sea turtles, spiders, or octopuses) while Milly patiently (or not) looks at a longer shot, taken in watercolor collage, of the newly-hatched penguin chick (alligator, duckling, etc.) in its natural environment. Posada's other books are about dandelions, ladybugs, and robins--she knows what we like!

[Nonfiction Monday Round-up at Anastasia Suen's blog Picture Book of the Day. Thanks, Anastasia!]