Story ID help

My SO is trying to find a book she read as a child, but can’t remember a title or author. I assured her, that if anybody could figure it out, it would be the Teeming Millions!

Here’s her description of it:

This book has stuck with me for almost 50 years and I’ve never been able to find it. I was 6 or 7, so it was 1958 or 1959. It was a library book. A small boy is ill and confined to bed, I think he has a fever or he’s healing from a broken bone. He’s drawing cartoons to amuse himself and when he falls to sleep the characters seem to take over and the action continues. When he awakens the story has moved along and he can see the results in the drawing on his sketch pad. It may be that the action alternates…he draws his part of the story and then when he falls asleep the characters respond… He has to outwit them in such a way that he’s safe while he sleeps? I think the characters included a monster as well as many toy soldiers. I think the illustrations were in black and white. I may be combining two stories into one… I remember being absolutely fascinated and also terrified! I would love to find this book again and see it through ‘adult’ eyes.
That ring any bells for anyone?

Thanks!!

The details don’t match exactly, but it certainly makes me think of the classic Harold and the Purple Crayon, which was first published in 1955.

“The Land of Counterpane” by Robert Louis Stevenson? The online versions of it I could find are pretty short, but I remember a really lavishly illustrated one from when I was a kid that seemed longer.

Close, but I think we’re still looking …