Penpal by Dathan Auerbach

In an attempt to make sense of his own mysterious and unsettling childhood memories, a man begins to reconstruct his past. As the games and adventures of his youth become engulfed by a larger story, he finds that it forms a tapestry of unbelievable horror that he never could have expected.

Each chapter completes a different piece of the puzzle for both you and the narrator, and by the end of it all, you will wish that you could forget what he never knew.