Your story is well-paced, and intriguing in the glimpses it offers into what is essentially Snape's obsession, as it changes objects from Lily to her son. It's honestly a little creepy, but very IC; I think Snape is a very tenacious personality, and given his history obsession isn't a big stretch. Your use of language is occasionally a little, what? stiff? I'm not sure, but there's a sense of strain there. Overall, however, your word choice and phrasing lend themselves well to the almost dream-like progression of the story, and your use of first person POV gives an immediacy to the narrative that's quite compelling.
I like your Harry, too, though he's in some ways relegated to the background. There's a clear sense of his personality--his devotion, his openness, his readiness to accept Snape's presence in his life, however peculiar his approach. And I'm always glad to see them get a happy ending.