I hesitate to tag this 'mystery' because the plot is so weak that I guessed the murderer halfway through (seriously, just halfway through) and knew why that character had done it three-quarters of the way through (with the exception of one tiny plot twist that was set up properly with a clue I'd forgotten about--the only good part of the plot). The other half of the mystery is just as obvious.
I'm not even sure this was meant to be a mystery. It's a lot closer to paranormal romance, which would explain why the mystery is given so little attention. It would also explain why I hated the love interest so much, since I've never read a single paranormal romance (or just plain romance) where I didn't loathe one or both of the main characters.
It's too bad about the plot (and the clumsy writing), because the set-up is great. M.J. Holliday is a psychic medium who lives in Boston* and works as a professional ghost-buster along with her computer hacker partner, Gilley-the-gay-sidekick. When Dr. Steven Sable hires them to investigate his recently deceased grandfather's hunting lodge, where strange things have been happening, M.J. has no idea that she's walking into a house full of old secrets--and a few new ones.
There are a lot of problems with this book beyond the plot. I liked Gilley, but halfway through he's conveniently put out of action and hardly appears in the rest of the book except to do some "hacking," and even then M.J. and Steven Sable find out almost all the same information Gilley does (thanks to a lot of coincidences and some breaking and entering). They also withhold information from Gilley for no reason that I could see. M.J.'s and Gilley's friendship has no depth beyond cheering each other on when it comes to picking up men. And while M.J. starts out as a strong character, she has that annoying weakness of paranormal romance heroines: her strength evaporates when a big strong man shows up. Steven Sable is an asshole, but she thinks he's hot so she forgives him for being patronizing, demanding, controlling, and secretive. Oh, and Steven Sable's difficulty with English words and idioms is annoying rather than funny.
The ending was the worst ending in any mystery I've ever read. Seriously, it was so bad I couldn't believe the editor okayed it. It's doesn't even make sense. Up until the ending, I was willing to put up with everything else because the parts with the ghosts are kind of interesting, but now this book is going to the used book store.
*of course she lives in Boston. What the hell? Are all books now set in Boston by law?