YA (I think) Fantasy. Boy and Girl invent fantasy world to escape reality. NOT Bridge to Terabithia. Possible spoiler

[AquaMoon]

Looking for a book I read...maybe 10 years ago, but the book itself may have been older. It centers on two children, a boy and a girl, who live out in the country and are neighbors. Both have hard home lives and they often go into the woods behind their homes to play. Here they invent an elaborate fantasy world filled with monsters and mythology. Seems the children were younger, not yet teenagers. I seem to recall they discover the boy's father is cheating on his mother with the girl's mother. I also recall the children were plotting to run away from home together at one point. I don't remember much else but that it was a very atmospheric, eerie story.

This is NOT Bridge to Terabithia but was similar in that it was about two children who created a fantasy world to escape the harsh reality of their home lives. I've searched around, but nothing sounds quite right.

Can anyone help?

[Joseph]

Maybe Too Far, by Rich Shapero?