Proof of Murder - Lauren Elliott

Bookshop owner Addie Greyborne must solve a locked-room murder in a supposedly haunted mansion to recover a priceless Sherlock Holmes original...
The seaside New England town of Greyborne Harbor is home to many grand estates, including the Queen Anne Victorian Addie inherited from her great aunt. Now one of those mansions is holding an estate sale, which is just what the bookshop owner needs to replenish her supply of rare editionseven if the house is rumored to be haunted. Assisting an overwhelmed insurance appraiser with the inventory, Addie discovers an 1887 magazine containing Arthur Conan Doyle's first Sherlock Holmes novel, A Study in Scarlet, which she estimates to be worth over one hundred and fifty thousand dollars.
But when Addie later finds the appraiser dead in the estate's private library, with the door bolted from the inside, and the priceless edition missing, it's a mystery worthy of the Great Detective himself. She's certain the death and the robbery are connectedbut who, other than a ghost who can walk through walls, could have gotten in to do the deed? It's up to Addie to find the key to the crimebefore she's the next one cornered by a killer....