Horace Slughorn, in all of his one dimensional (lack of) glory, was one of my least favorite JKR creations. But the wry, sly voice you have given him here adds such depth and shading to his character that I have changed my mind. *This* is a Slughorn I'd be interested to know, and I can understand thoroughly why Irma sees in him.
I love, too, the cameos of staff and students, the suspicions Horace has about what the message his last (living) conversation with Dumbledore was meant to imply, his perspicacious observations concerning Dumbledore's funeral, and the ruminations on all of the ways he could/should have begun his courtship of Irma, the view of our dear librarian through a very different lens than the one from which we are used to seeing her, and the perhaps not surprising revelation that Dumbledore is a better interlocutor dead than alive. :-)
But most of all I love this: But it isn’t sweet. It’s glorious. It’s a field of sunflowers, a lark rising to a blue, blue sky. It’s the sound of trumpets, the smell of spring mornings;it’s the roar of the ocean. It’s thunder and lightning.
It’s Horace Slughorn, that discerning reader, who doesn’t give a damn he’s trotting out every cliché under the sun.
For these are only clichés when you talk about others. Not when it’s about us, for I tell you, Albus, and you had better believe it, I tell you that no-one, in the whole history of mankind and wizardkind, has ever felt quite like this before. Was there ever a better summation of the way being in love makes one feel? Thank you for this lovely little gem of a fic, Mystery Author!