I enjoyed this book. It's pretty typical urban fantasy fare, and some of the plot elements reminded me strongly of Kim Harrison's Hollows series. Ashwood doesn't really do anything new or interesting with the genre (aside from suggest the reason that supernatural beings "came out" was because it was just too hard to stay hidden in today's electronic world) but it's still a fun popcorn book.
Holly Carver is a witch who has lost the ability to do big-M magic as opposed to small-m magic (the book's terms). She earns money by doing low level stuff, clearing out ghosts in houses, etc. (One interesting concept is that the houses of witches gradually become sentient). Her partner is a vampire named Alessandro Caravelli. She also has a human boyfriend who is uncomfortable with magic.
Hell is actually a prison constructed thousands of years ago by human magic users to imprison every other supernatural creature. Now some of them want to get out and Holly and Alessandro have to stop them.
Ashwood has also constructed a world where a Chosen one (a lover and beloved of a vampire) can make it so that a vampire doesn't have to live on the blood of others but can live off the love of his or her Chosen. No prizes for guessing how that turns out in this story.