Ghoul Interrupted (Ghost Hunter Mystery #6) by Victoria Laurie.
The last time we saw the Ghost Hunters crew, they were in Ireland removing a phantom from a castle. There is a possible basis for a show in Dunkird, but they have to put aside these plans and head to New Mexico to deal with the death of Heath's Uncle Milton.
M.J.'s spirit guide Sam Whitefeather (who happens to be Heath's grandfather) appears in a dream to warn her of this just before Heath is notified by his cousin. Sam informs M.J. that Milton has been unable to cross over because of the traumatic nature of his death, which was caused by a demon whose mission is to destroy the Whitefeather clan. M.J.'s job is to locate the person possessed by the demon and kill him or her.
Although M.J. is not thrilled about the idea of killing someone, she's prepared to do it if it's the only way to dispose of the demon. While Gopher and the rest of the Ghost Hunter crew return to L.A. to deal with paperwork, M.J., Heath and Gilley fly to Santa Fe to take care of the evil spirit.
M.J. and her crew fight ghost and demons the same way one would fight any battle, by being mentally prepared and having the proper tools and weapons (which include custom magnetized spikes and "grenades"). Laurie's matter-of-fact narration of these astonishing events is what keeps this series from edging into the horror novel category.
At the end of the book is a preview of the next Ghost Hunter novel What A Ghoul Wants, due in January 2013.
*FTC Full Disclosure: Many thanks to the publisher, who sent me a copy of the book for review purposes.