It's even better than the first time. I have a folder on my hard drive of fics that I've copied to save, fics I go to read when I need to clear my palate and fall in love all over again, and remember why I write Snarry. This one's going in there.
Reading, it didn't even strike me until afterwards that there was no magic. They're still so intensely Snape and Harry, their canon personalities shine through all those bantering conversations--Snape a bit softer (but not much), and Harry a bit more mature. Each of those scenes builds upon the other so that the end isn't a stretch at all. I love that Severus left a clue, and that Harry took a chance.
Lochinvar and your title thrilled me to my toes, too! How perfect!
Having spent a great deal of my life in hospitals at night, I can't tell you how believable even the premise of such a friendship being forged struck me. *happy sigh*. Great job, very well done, Perfica.