The Dark Heart of Time: a Tarzan novel is a 1999 work by Philip José Farmer

Philip José Farmer

Philip José Farmer was an American author, principally known for his award-winning science fiction and fantasy novels and short stories....

 authorized by Edgar Rice Burroughs, Inc.

Edgar Rice Burroughs, Inc.

Edgar Rice Burroughs, Inc. is an American company founded in 1923 by author Edgar Rice Burroughs. It is based in Tarzana, California. The company holds the rights to the literary works of Burroughs that are still protected by copyright .Burroughs was one of the first artists to...

 The book was first announced under the title Tarzan's Greatest Secret in 1997.

Set in October 1918—during Tarzan's search for Jane—the novel takes place between Tarzan the Untamed

Tarzan the Untamed

Tarzan the Untamed is a book written by Edgar Rice Burroughs, the seventh in his series of books about the title character Tarzan. It was originally published as two separate stories serialized in different pulp magazines; "Tarzan the Untamed" in Redbook from March to August, 1919, and "Tarzan and...

and Tarzan the Terrible

Tarzan the Terrible

Tarzan the Terrible is a novel written by Edgar Rice Burroughs, the eighth in his series of books about the title character Tarzan. It was first published as a serial in the pulp magazine Argosy All-Story Weekly in the issues for February 12, 19, and 26 and March 5, 12, 19, and 26, 1921; the first...

.

The novels antagonist is James D. Stonecraft, an American oil magnate who believes that Tarzan knows the secret of immortality. Stonecraft hires hunters to track and capture Tarzan for the secret, leading to a conflicts at the "City Built by God" and the "Crystal Tree of Time". Through all of the adventure Tarzan is focused on escaping his pursuers so that he may return to his search for his wife.

More Tarzan by Farmer

Best known for his Riverworld

Riverworld

Riverworld is a fictional planet and the setting for a series of science fiction books written by Philip José Farmer . Riverworld is an artificial environment where all humans are reconstructed. The books explore interactions of individuals from many different cultures and time periods...

 series, before the Dark Heart of Time, Philip José Farmer wrote a number of books based to some extent on Tarzan.

• Time's Last Gift (1972) being a time travel story, the novel is both an unauthorized sequel to the entire Tarzan series, and a prequel to the authorized Khokarsa series.
• Tarzan Alive: A Definitive Biography of Lord Greystoke
  Tarzan Alive: A Definitive Biography of Lord Greystoke
  Tarzan Alive: A Definitive Biography of Lord Greystoke is a fictional biography by Philip José Farmer. It presents the life story of Edgar Rice Burroughs' literary hero Tarzan as if he were a real person....
  
  (1972/2006)
• The Adventures of the Peerless Peer (1974) an unauthorized work in which Tarzan meets Sherlock Holmes
  Sherlock Holmes
  Sherlock Holmes is a fictional detective created by Scottish author and physician Sir Arthur Conan Doyle. The fantastic London-based "consulting detective", Holmes is famous for his astute logical reasoning, his ability to take almost any disguise, and his use of forensic science skills to solve...
  
  .
• Khokarsa series, novels authorized by ERB, Inc. set in Tarzan's Africa 10,000 years ago.
  • Hadon of Ancient Opar
    Hadon of Ancient Opar
    Hadon of Ancient Opar is a fantasy novel by Philip José Farmer, first published in paperback by DAW Books in April 1974, and reprinted three times through 1993. The first British edition was published by Magnum in 1977...
    
    (1974)
  • Flight to Opar
    Flight to Opar
    Flight to Opar is a fantasy novel by Philip José Farmer, first published in paperback by DAW Books in June 1976, and reprinted twice through 1983. The first British edition was published by Magnum in 1977....
    
    (1976)