The Lamp from the Warlock's Tomb (Anthony Monday Mystery)

Anthony Monday can't understand why his best friend Miss Eells, the town librarian, is so excited about an old Dutch oil lamp, but she buys it anyway. Little do they know that the lamp was stolen from an underground tomb--a frightening place where eerie occult rituals used to be held. When Anthony borrows the lamp for a school science project, he makes a very big mistake: he lights it. Monstrous forces are at once unleashed, forces so demonically powerful that they threaten to take over the entire world--unless Anthony and Miss Eells can stop them! -- From back cover of Bantam-Skylark edition, 1989