Over and Over by Charlotte Zolotow, illustrated by Garth Williams (1957).
While of course I'm a fan of both the author and illustrator, I hadn't read this book until recently. I found it online and thought it sounded lovely so decided to buy it. I'm glad I did. It's a simple story of a little girl who is too young to understand time, so each month her mother helps her look forward to the holidays and seasons. The text and illustrations are wonderfully evocative of early childhood.
