Ooh, I do so love a good haunted house tale! It certainly sets the mood (a collection of individuals who WANT to stay in a haunted house for whatever purpose--think Haunting of Hill House), and while it delivers on building creep factor, it rarely delves into outright horror. The true appeal comes from its thrilling storytelling independent of actual frights, though there are plenty of those, too. When the group starts getting picked off one by one, yikes, things are ramped up till the very end. Delish! 4 stars.
Easy to read, but I thought there were a few too many things I didn't like to recommend it. The first 2/3rds are a typical haunted-house tale, where strange, possibly supernatural, things happen. The last part is sort of way over-the-top, like a slasher movie script. I found myself skimming much of the last 100 pages (in a too-long book.) For a more satisfying haunted house read, try Dorothy Macardle's The Uninvited, or Michael MacDowell's The Elementals.