Haunting of Room 909 (Junior Paranormal Investigators #1)

Summer is usually a time of fun and games for most children, but Hanna and Ben Littleton are not your average eleven and twelve-year-old. Their father is Percy Littleton, a famous paranormal investigator, and this summer they are traveling to different locations to investigate unexplained phenomena. Things are rather boring until they stop at Castleridge Hotel.
Though warned by their father not to meddle in his investigation, the brother and sister are convinced they can prove their worth as true investigators. Their eagerness soon turns to terror when Hanna begins having visions about a certain former employee of the hotel, the elevator takes them to the ninth floor on its own, and ghosts interact with them. The building seems to have a mind of its own as Hanna and Ben are forced to figure out what really happened one hundred years ago at Castleridge Hotel, before the spirits trapped inside decide to make them permanent residents.