I read this book in the 1980s and it was almost certainly a children’s book, but a real novel. It was set in Europe I believe.

Long ago a boy lost his parent in a nearby forest. The forest is malicious and very difficult to walk deep into. As you walk into the forest, the placement on trees you had to walk around would gradually turn you back so you exited. Several years after the lost parent the boy has grown up and is determined to enter deep into the forest. He hires an airplane to take overhead photos but winds blow it away. Eventually he does make it to the center and there’s some kind of mystery. I felt it was very well written, a thriller, and scary, too. It seemed to have been set in the 1950s. I hope that’s enough. I’d love to rediscover this book and was glad to pay the fee! Thank you! 🙂