This is #9 in Castle's Ghost Hunter series.
She kind of phoned this one in. There were sections of the book where Castle (aka Krentz) couldn't be bothered with a believable back-and-forth conversation between the lead characters. One would ask a question (What did you do?), and the other would then just lecture for a page or two. And then they would do it all over again: a leading question with paragraphs of monologue. No sense of people actually interacting or communicating with each other.
Why else do we read her?
The plots are completely predictable; doesn't bother me. The blathering about the various types of energy and ability to view or manipulate same, I just ignore. The fact that the villain is going to spill everything at the climax - in chronological order, no less - and laugh maniacally while doing so, no worries.
I read her books for the characters and their conversations. The romantic leads are always people that are involved with others, take care of their responsibilities, don't whine, never use tragedies of the past as an excuse not to live: in other words, adults with whom I like spending time. Their conversations with each other (and the occasional pet or dust bunny) are why I read her, and have for years.
And why I will buy the next book, even though I was disappointed with this one.