The Lamp from the Warlock's Tomb — John Bellairs

A murderous surprise comes to light in this thrilling mystery featuring teenager Anthony Monday, from the author of The Dark Secret of Weatherend.
 
Ever since librarian Myra Eells bought an antique oil lamp, weird things have started to happen in Hoosac -- including the murder of a high school maintenance man. Anthony Monday is convinced it's haunted, but Miss Eells thinks he's just being silly -- until she sees a terrifying vision.
 
When they call in Miss Eells's brother for help, they learn that the lamp has been stolen from the strange tomb of a Wisconsin lawyer who was involved with the occult. Convinced that evil forces exist inside the lamp, the trio plans to return it to the underground vault. But someone else will do whatever it takes to steal the lamp -- and unleash a dark and ancient power upon the world . . .
 
“Half-mockingly using the colloquial style made familiar in such series books as the Nancy Drew stories, Bellairs keeps the action moving right along.” -- Kirkus Reviews