Okay, I feel like if I'm the first reviewer I need to say something more coherent.
I was thrilled when I saw the summary, because this is what I've been wanting to read, but I really enjoyed watching the way the paradox played out. It's always interesting in time travel fics to see the navigation between missing the old life and integrating into the new one, plus how the time traveler deals with trying not to disrupt the time continuum. The biggest strength to this story, IMO, was keeping it romantic and still realistic. Severus still has hormones and is still pragmatic, Harry isn't all moony or anything. I liked the build, and I liked Severus' quick thinking in the library.
I will say the one weakness (not that I minded this at all) was the frame, because I didn't really feel like Harry was all that torn up about losing his old life. It's as if Harry is researching it but disassociated. I just re-read No Way Back the other day (not lying about being on the time-travel kick!) and I think the pull of the old life was much stronger and more realistic in terms of Harry's coming to terms. Of course, this story was told over a longer period of time.
Anyway, sweet!Severus was great, and this really hit the spot.