_A_Legacy_of_Daemons_ by Bacon-Smith is part of an ongoing series. Not having read previous books in the series, I can say that this book stands up pretty well on its own.
While it is set in the present day, Bacon-Smith's Earth is the result of a cosmic accident. It is the result of an unintended breach between the second & third heavenly spheres. While humans are vastly weaker than the daemon lords of the seven heavenly spheres, humans are also the only creatures in the spheres that take material form & some humans have the ability to summon daemons to earth & bind them here. (The daemons in question are not evil demons, but angels & demons and God & Satan do also exist in Bacon-Smith's creation as well.)
The main character is Evan. He is half-daemon and there are a number of daemons and other supernatural beings who would be happier if he was just killed off. As a human, he has a connection to the third sphere (it was curiosity of the denizens of the third sphere that created a hole between the spheres and earth is the patch that fills that hole, so all humans are part of the third sphere in a way) but his daemon half comes from a daemon parent of the second sphere, so theoretically if anyone is going to re-open the hold between the second and third spheres it would likely be Evan.
I gather that in previous books, Evan was unaware of his half-daemon side, but was kidnapped & tortured by those who were, so on the whole was quite insane for a good part of his life. He is now sane -- although prone to distressing flashbacks at times -- and has formed a detective agency with Brad/Badad and Lily/Lirion. Brad & Lily are the human names for Badad & Lirion, two daemons of the second sphere. Badad is Evan's daemon parent; both he & Lirion protect Evan as well as evaluate him to decide if he indeed should be killed after all.
The book begins with Evan being approached by a daemon of another sphere, bound in human form, who wants to commission the detective agency to purchase a chest that is coming up at an estate auction. Things are not always what they seem, there's a family who have been summoning & binding daemons since the Black Plague, and there's lots of other secondary players too.
The writing is great, and the writing by itself would get five stars. But the plot, pacing and characterizations . . . at times great, at times not that great. To me Lily/Lirion was pretty much a cipher. She likes stealing stuff because it's a challenge, she enjoys having sex with Evan because human bodies are designed to enjoy sex, she has a bad temper and she hates priests because one tried to bind her in a Russian forest a couple of centures back. That's it. She really is a non-human otherworldly creature who wears a human body for a while but is fundamentally not human. Brad/Badad, even though he is a daemon, during the course of the book starts to experience some emotions that come dangerously close to human. He worries about Evan; at one point meeting someone who mentions they know what Evan is and have been keeping their eye on him for a number of years, all Brad/Badad can think of is "you watched for *years* while my son was held hostage & tortured and did *nothing*???" in a red rage. There comes a point during the book when both Brad & Lily are convinced that Evan has been killed. Lily wants to start a war between the spheres & wipe all life off earth and be done with it, while Brad wants to find the specific person who killed Evan. The other daemon lords of the host of Ariton -- Brad/Badad's & Lily/Lirion's daemon Prince -- become so concerned at Badad's increasingly human feelings that they begin to shut him out of deliberations of the host of Ariton. Lirion is still a member of Ariton in good standing.
And that brings up the other thing that after a while starts to raise some serious questions about the whole premise: daemons are horrendously powerful supernatural beings. Daemons are so powerful that one angry demon should be able to completely eliminate a fairly large city, and a host of angry daemons can destroy all life on earth without even tiring themselves out. Humanity & the material world occasionally intrigue them, but to be bound to the human realm or to a material body is torture to a daemon. But humans *are* summoning & binding daemons, and have been since at least Roman times. So, on the one hand, there is this constant worry by the main characters of not angering this or that daemon host, or finding a way to safely bind or release an angry daemon, and it's all very important because daemons are so powerful. But if daemons are so powerful and quick to anger, how in the world has humanity survived until now? It's like reading a book where humans discovered how to make nuclear bombs back in the 1200s and has been making them every generation since then but miraculously not once in 800 years has anyone ever set one off.
So, the writing is five stars, but the plot and characterizations and pacing (the book drags a bit around the middle) are three stars. So I'm averaging it out to four stars.