Eidolon by Grace Draven

I almost do not have words; I stopped reading this twice because I became so afraid that something irreversibly terrible was going to happen to either Brishen or Ildiko who, individually and as a couple, are just <chef’s kiss>. This sequel, the first book, they’re so good. 

A synopsis without spoilers (as long as you have read the first book): 

After shadow demons have been summoned and try to take over the world, our MMC has to turn into a wraith king to defeat them, leaving our FMC to rule over a kingdom full of Kai who want to kill her human ass. Also, our two main characters, who love each other very much, might not get to stay married because a human and a Kai can’t make a baby heir which is important for reasons. 

It gave me so much anxiety the whole time. I cried. But like in a good way. I mean, is it just me or are we all as invested in this couple as I have ever been in any book couple I have ever read about ever? Like, ever ever.