He is best known for The Necromancer; or, The Tale of the Black Forest, an English translation by Peter Teuthold of his Der Geisterbanner: Eine Wundergeschichte aus mündlichen und schriftlichen Traditionen, which is one of the seven 'horrid novels' referenced by Jane Austen in Northanger Abbey.
[4] German gothic tales were the major contributor to the genre in England in the 1790s, with Kahlert's standing among them, alongside Cajetan Tschink, Carl Grosse, and Veit Weber.
[4] The Necromancer was a bestseller, and famous enough that it was included in the list of 'horrid novels' in Northanger Abbey alongside The Castle of Wolfenbach by Eliza Parsons, Clermont by Regina Maria Roche, The Mysterious Warning, a German Tale, by Eliza Parsons, The Midnight Bell by Francis Lathom, The Orphan of the Rhine by Eleanor Sleath, and Horrid Mysteries by Carl Grosse.
[7] Critic and writer George Saintsbury was a prominent disbeliever in the authenticity of the septet, stating: "I should indeed like some better authority than Miss Isabella Thorpe's to assure me of their existence.
[8] The rediscovered copy of The Necromancer came from the estate of Arthur Hutchinson, a magazine editor and book collector, who bequeathed his library to Sadleir upon his death.