This is the one. The book that started it all. And the original cover (or at least part of it). Scholastic has re-released the book with some funky new cover, but I like the old one best.
I first read 'The Forgotten Door' by Alexander Key in 5th grade. I had Mrs. Milan in Riverside, California and she pretty much let me read whatever I wanted.
(That was the year I read through the set of encyclopedias on her classroom shelf. Yes, I was that weird.)
However, The forgotten Door was part of the curriculum, and I LOVED it.
A kid gets lost through some old teleportation/time-travel door, and stuck in our world. He deals with suspicious small-town people, guns and our judicial system. His telepathy makes it possible for him to communicate with the family who finds him and helps him, but can't stop the legal system from trying to 'protect' him.
Up until this point I had read a lot of Nancy Drew/ Trixie Belden type stuff. After this, I was transported into C.S. Lewis' The Lion, The Witch and The Wardrobe type stuff.
I discovered my niche. My comfort zone. My happy place.
I re-read this book last week, and discovered it has stood up to the test of time. It's still good.
Mind you, I wasn't as enthralled as my 9 year old self, but the story itself is good. I could see/remember why I loved it so much.