I really liked how this wasn't exactly time-travel, but it's a Harry/Young Snape story. Very original concept, how he ended up there. It's always interesting to read Snape before he's become so embittered, and to read a story like this, where Harry has something to do with changing that was satisfying. Really was afraid when Hermione couldn't find Harry in his bed--sort of reminded me of Back To the Future when Marty's family started to fade from the picture--something had to be done, and Harry was really very lucky that she discovered what was happening; otherwise, he might've ended up 'stuck' without a choice. In the end, though, having to make that choice was what would make it all work, I think, so far as Harry and Snape were concerned.
Enjoyed the inclusion of Harry's friends, their conversations, and especially Albus in the Marauders' time. It sort of messes with my mind, thinking that another Harry will be born, and who will actually fight Voldemort?
Well-written, and once I started reading, I was propelled onward! Great job!