Aileen Fisher's KNOW WHAT I SAW? is the Perfect Counting Book
Actually, it’s a countdown book since the counting is backwards - from ten down to one.
What makes it perfect (for ages 2-5) is the illustrations by Deborah Durland... combined with a wonderful and effortless pattern of rhymes throughout.
It’s just the kind of book a grandfather can enjoy reading aloud to a lapful of the next generation.