In Why Does the Moon Change Shape?, Isaac Asimov carefully and clearly explains the Moon’s bewitching ability to wax and wane.
For general information on the “Ask Isaac Asimov” series, see What Is a Shooting Star?
There’s little to say about this book. It’s too expensive, but very elaborate and well-illustrated. It’s excellent for young children who want to know a bit about astronomy. Just don’t actually buy it.