I Read Books: Seduced By Moonlight
Merry Gentry, the American Fairy Princess, has sex with several magical people which restores, or in some cases unleashes their power, later there’s an assassination attempt when she returns from LA to the fairy mounds near St Louis for Yule. The mounds themselves start to come back to life. Her Aunt, the Queen, is drugged into a frenzy, and they get into a fight, and Merry’s blood powers suck all her blood out including the drug so she recovers.
That’s most of the plot, though sometime the having sex isn’t having sex but is about blood, or being nearby while she has sex with others, or touching the magic fertility ring. Also the Goddess gets involved, giving visions while restoring powers, handing over the chalice (formerly the cauldron) in a dream etc. Also Merry meets a lot of people, mostly men, most of whom she will have to have sex with (as the sidhe are fairly infertile she can only become queen if she has a child). A couple she is barred from having sex with though.
Basically everything gets rather complicated, the cast of characters expands, Merry has to deal with all of the men who want to have sex with her for various reasons (politics, magic, power, lust and even love), with no indication that anything will be resolved soon.
Read This: Because you were into Merry’s story of magic and politics and sex
Don’t Read This: If you wanted more of her trying to balance being a private investigator with being a princess (spoilers, she gives up on the PI bit as far as I can see)