I think this book is probably the most successful attempt I’ve read (not…that I have read many) at reconciling the dual desires of readers to a) have the lesbians b) wear the corsets. The other paradox that readers want is aristocracy romance + sex, and you usually get there by having the woman not be a full on virginal lady but instead some sort of exception case (like: widowed, openly an escort, lacking a chaperone who would care).
So here, the escape valve is a bit two fold. On one hand we have Tommy/Thomasina, one of a motley crew of orphans adopted by an eccentric but uber rich Daddy Warbucks esque figure who have a Quirk apiece and will all, of course, end up wealthily and happily married (or paired off). By this book, #2, there’s already one sister who is now a Duchess, giving a veneer of real respectability to her assorted siblings who are most decidedly not welcome in Polite Society. On the other hand we have Phillipa, who is merely as wealthy as Croesus (i.e., not nobility herself) and able to explain away all her foibles through being a bluestocking.
While the cover gives away the plot (Phillipa + Tommy forever) it does paper over how queer, exactly, this novel is. Tommy is genderfluid, a topic which Phillipa takes in stride (as a matter of fact, she very logically and non-judgementally assumes when Tommy first tries to explain her gender identity that Thomasina was born Thomas but is actually Thomasina). So it may be anchronistic, but Phillipa’s acceptance of Tommy–and the ways in which she hurts her, and how she learns that they were hurtful and does better–are well handled if a bit too choreographed (how many times do you need to hear Phillipa talk about her cold heart to telegraph that clearly she’s going to find that it’s not her heart that’s the issue but the gender of the people she’s trying to give it to).
Which is to say, this is a book without content warnings despite being about a cisgender female/cisgender genderfluid-female-leaning lesbian couple in Ye Olde England times.
There’s also a plot about a cipher and an illuminated manuscript and light temporary thievery, I can’t really say I retained all of it in great detail because that’s not the point of this story. You’re much more invested in their small, human interactions between Tommy and the rest of her Wild Wynchester siblings (the bittersweet pain of losing a sibling to a marriage, in particular, is well done).