Ho Yay: So, so much of it, whether it's involves them touching, comforting one another, having intimate conversation, or Laurent pining/admiring Aymar's looks and personality. Laurent's feelings start off as hero-worship and grow over the course of the novel to outright adoration, and Aymar is, needless to say, very grateful.
Laurent is quick to think ill of anyone who hurts or talks badly about Aymar, and even shows dislike towards Aymar's potential love interest(s).
And, thought M. de Courtomer with all the worldly experience of four-and-twenty, as Mme de Morsan's languorous expression and half-mocking smile smote themselves into his perceptions, 'if ever a woman was set on a man, she is on him!' But he hesitated to add that the reverse was true, for L'Oiseleur was undisguisedly frowning at her, with that peculiarly straight gaze he had when he was angry-as witnessed by Laurent in his own dining-room across the Channel. Unless, of course, it was a lovers' quarrel. They made, indeed, a most striking pairbut somehow he did not want... How ridiculous for him to assume a critical attitude to the Vicorate de la Rocheterie's affaires de caeur... if he had any.
Hurt/Comfort Fic: Much of this story resembles modern day hurt/comfort slash fanfiction.
Narm: This book can get pretty smarmy, to the point of being ridiculous.
At one point, Laurent captures a grasshopper outside and announces to Aymar that he's going to tame it. He names it Vert-Vert (literally, "green-green").
Aymar to Avoye: "Your mouth is like apple-blossom!"
Melodrama: A good amount through the whole book, but especially in the last third after Aymar meets with Avoye again.
Squick: Modern readers might find Avoye/Aymar off-putting because they are first cousins, and there's a lot of emphasis placed on the fact that they were raised as siblings after their parents died. It should be noted that their grandmother, who raised them, very much supports their relationship, and no one in-universe considers their love to be taboo.