1) That cover. THAT COVER!!! a Polynesian main character! The actual cover looks a tad white-washed, but here's the non-cropped version provided by the author on her Tumblr
2) yes, it really is historical fantasy (my favorite genre!) A purist might argue it's set in a mirror of Victorian/Imperialist England, but I'm running with it.
2) magical shadows and magical books that can turn into birds. Sir Bird!
3) magical doorways (a la Howl's Moving Castle) (in fact it was the "Howl's Moving Castle meets Mr Darcy" blurb that caught my eye with this book... well, that and the cover. And Laini Taylor's whole-hearted endorsement didn't hurt either).
4) delightfully witty old fashioned ink letters, complete with ink blots
5) oh, and some of the letters are ALSO magical (those written by whom I cannot spoiler-name)
6) Jane Austen-worthy observations on English (I mean Alben) nature:
An Alben smile is rarely and expression of joy. More often it is a way to deflect true emotion.
7) magical miniature suns (yeah, there's a lot of fun magic in this book)
8) excellent recrafting of real empire/colonial issues:
His words strike straight through me. I would have said the same thing just weeks ago. I would have dismissed an entire country of people just because of their birth, the same way I have always felt dismissed.
9) magically-colored music
10) magic hair-color-turning wars (reminded me of the fairy wars over the color of Aurora's dress in Sleeping Beauty)
11) Fifteen different words for love, but one of them forgotten until the end
12) Collarbones (you never realized how interesting they were till now)
13) Using math to mess with dreams
14) Eleanor's gossip
15) the gift of an umbrella on a rainy day from a kind stranger in a park
16) Lord Finley Ackerley and his cane, and how he loved Jessamin even though she insisted on doing the opposite of everything he ever suggested