Necroscope #1-5 & The Vampire World #1-2

Necroscope is the title of a series of horror novels by British author Brian Lumley.
The term necroscope, as defined in the series, describes someone who can communicate with the dead (coined Deadspeak later in the series). Unlike necromancers, who attempt to command the dead through rituals, spells, bodily mutilation and sometimes necrophilia, a necroscope simply communicates with them without any physical interference.