My Side of the Mountain was a Newbery Honor Book in 1960. It is still popular and in print in the US, although I suspect that it is much less known on this side of the Pacific.
I can see why this tale of an independent, capable lad like Sam Gribley spending a year living alone in a tree in the Catskill Mountains is so popular with children. It's a great adventure tale. Sam runs away from his apparently loving family in New York, where he is one of 9 children, to eek out an existence, eating plants he finds in the forest and killing his own prey. He even befriends a young peregrine falcon, which he names Frightful (perhaps the best named pet ever?), and uses her to help with his hunting.
There are quite lengthy and detailed instructive sections about how to survive in the wild. How to whittle your own fish hooks. Diagrams even of the plants he eats, and recipes for the meals he eats such as frog soup. I'm sure countless child readers have dreamed that they too would run away from their family and survive in the wilds, using their wits, muscles and skills.
The writing style is quite simplistic, written as it is almost in diary form of a 12 year old boy. There are some special passages though.
Frightful would awaken, I would feed her, she would fall back to sleep, and I would watch the breath rock her body ever so slightly. I was breathing the same way, only not as fast. Her heart beat much faster than mine. She was designed to her bones for a swifter life.
Nearby another one arose and there was a pop. Little bubbles of air snapped as these voiceless animals of the earth came to the surface. That got me to smiling. I was glad to know this about earthworms. I don't know why, but this seemed like one of the nicest things I had learned in the woods- that earthworms, lowly, confined to the darkness of the earth, could make just a little stir in the world.
Later in the book there are a number of reflections about loneliness. By this stage Sam has spent the better part of a year living on the mountain. So it is natural that he consider it. But Sam does not get lonely. He has the occasional visitor, both two and more legged. And he befriends Frightful and Baron Weasel.
The human being, even in the midst of people, spends nine-tenths of his time alone with the private voices of his own head. Living alone on a mountain is not much different, except that your speaking voice gets rusty.
There are some rather literary references. A stranger Sam meets dubs him Thoreau, and later quotes Dickens. Sam himself is rather mindful of nutrition. He recognises that winter restricts his diet and puts him at risk of deficiency. A nose bleed in January makes him worry about his health. He learns that liver is a useful source of vitamin C, and uses that to stave off scurvy. Very interesting to note on Wiki, that most animals synthesise their own vitamin C. And that scurvy develops after just 3 months of severe or complete dietary vitamin C deficiency. Which makes sense for a water soluble vitamin.
I did find it slightly hard to suspend belief that his family left him alone, and the numerous adults that he told what he was doing let him be as well. I didn't really like the ending to the book, finding it much too implausible, but overall I did enjoy my time with My Side of the Mountain. It was also an interesting contrast to From The Mixed Up Files of Mrs Basil E Frankweiler which I read recently. There a young girl, Claudia, ran to New York, specifically the Metropolitan Museum of Art. Here, a young man runs from New York. I love timing like that.