I found this to be a lovely gentle story set in a time that doesn't exist any more. I'm not of the age to remember these times, but I've heard stories of my mother's childhood running around without a care in the world, out from dusk 'til dawn. Gerald has a close-knit family, but he doesn't quite fit in with his older siblings. They have to share not just rooms, but beds when the extended family comes to stay, so he has to find someone he trusts to help care for Gerald as he doesn't want to tell anyone about his new friend.
I think this story is aimed for children, however, I love reading books for any age and this was enjoyable from a grown-up's perspective. Whenever I put it down I was wondering what would happen to Douglas the caterpillar next.
Even though this is Gerald's story, his family's stories were just as enjoyable and it all came together in the end.