I really enjoyed The Impossible Fortress by Jason Rekulak. The story is based around the same time that I grew up, so I appreciated and recognized lots of the historical details and setting in the story. Plus, I like technology and games and programming, so the story was fun to read and unique. If there is a negative part, I would say it is the swearing in the dialogue. I realize this is probably pretty accurate for some teenagers, but I know I didn't talk like this. So, at times, it was awkward to imagine young kids saying some pretty disgusting things. But, again, overall, I really liked the story. I hope to read more about Billy and Mary. Finally, it is pretty cool that the author worked with a team to create a real version of the game talked about in the story.
You can play it here: http://jasonrekulak.com/game/