Question: Enemy at the Gates portrays the character Vasily Zaytsev, and is based off which book?
Context: Enemy at the Gates is a 2001 French-American war film written and directed by Jean-Jacques Annaud and based on William Craig's 1973 nonfiction book "", which describes the events surrounding the Battle of Stalingrad in the winter of 1942 and 1943.  The film's main character is a fictionalized version of sniper Vasily Zaytsev, a Hero of the Soviet Union during World War II.  It includes a snipers' duel between Zaytsev and a "Wehrmacht" sniper school director, Major Erwin König. The Hot Gates is the title of a collection of essays by William Golding, author of "Lord of the Flies".  The collection is divided into four sections: "People and Places", "Books", "Westward Look" and "Caught in a Bush".  Published in 1965, it includes pieces that Golding had written over the previous ten years.  "Caught in a Bush" contains his childhood recollections "Billy the Kid" and "The Ladder and the Tree", and his essay "Fable", which answered questions about "Lord of the Flies" appears in "Books".  "Fable" is based on lectures Golding gave at UCLA in California and he hoped it would answer "some of the standard questions which students were asking" (7).  The book starts out with an essay on the Battle of Thermopylae, which can be translated from ancient Greek to English as "hot gates", thus giving it the title.  The Hot Gates are famous for being the place where Leonidas I made his last stand against the Persian army under Xerxes I. Jens Peter Daniel Bogren is a record producer, mixer and recording engineer who has worked on albums by Opeth, Dimmu Borgir, Sepultura, Arch Enemy, At The Gates, Katatonia, Babymetal, Soilwork, James LaBrie, Moonspell, God Forbid, Kreator, Devin Townsend, Ihsahn, Dark Tranquillity, Paradise Lost, Amon Amarth, Dragonforce, The Ocean, Haken, Rotting Christ, Symphony X, Myrath, Angra and Dir En Grey amongst others.  Bogren lives in Örebro, Sweden and is based at Fascination Street Studios. The Book of Gates is an Ancient Egyptian funerary text dating from the New Kingdom.  It narrates the passage of a newly deceased soul into the next world, corresponding to the journey of the sun through the underworld during the hours of the night.  The soul is required to pass through a series of 'gates' at different stages in the journey.  Each gate is associated with a different goddess, and requires that the deceased recognise the particular character of that deity.  The text implies that some people will pass through unharmed, but that others will suffer torment in a lake of fire. Vladimir Petrovich Filatov (Russian: Владимир Филaтoв , 15 [O.S. 27] February 1875, Mikhaylovka, Penza Governorate, Russian Empire - 30 October 1956, Odessa, Ukrainian SSR) was a Russian and Ukrainian ophthalmologist and surgeon best known for his development of tissue therapy.  He introduced the tube flap grafting method, corneal transplantation and preservation of grafts from cadaver eyes.  He founded the Institute of Eye Diseases & Tissue Therapy in Odessa, Soviet Union (today Ukraine).  Filatov is also credited for restoring Vasily Zaytsev's sight when he suffered an injury to his eyes from a mortar attack during Battle of Stalingrad. Vasily Grigoryevich Zaytsev; 23 March 1915 – 15 December 1991) was a Soviet sniper and a Hero of the Soviet Union during World War II.  Prior to 10 November, he killed 32 Axis soldiers with a standard-issue rifle.  Between 10 November 1942 and 17 December 1942, during the Battle of Stalingrad, he killed 225 enemy soldiers, including 11 snipers. Pirates of Silicon Valley is an original 1999 American made for television biographical drama film, directed by Martyn Burke and starring Noah Wyle as Steve Jobs and Anthony Michael Hall as Bill Gates.  Spanning the years 1971–1997 and based on Paul Freiberger and Michael Swaine's 1984 book "Fire in the Valley: The Making of the Personal Computer, "it explores the impact of the rivalry between Jobs (Apple Computer) and Gates (Microsoft) on the development of the personal computer. Erwin König and Heinz Thorvald are names of an apocryphal Wehrmacht sniper allegedly killed by the Soviet sniper Vasily Zaytsev during the Battle of Stalingrad. Tania Chernova was a Russian-American who claimed in interviews to have been a trained sniper for the Soviet forces during the Battle of Stalingrad.  However, the historian Antony Beevor has questioned the veracity of her claims and described her as a "fantasist".  A character, played by Rachel Weisz, based on Chernova, appeared in the film "Enemy at the Gates". Enemy at the Gates: The Battle for Stalingrad is a book written by William Craig and published in 1973 by Reader's Digest Press and in 1974 by Penguin Publishing.  The 2001 film "Enemy at the Gates" utilized the book's title and used it as one of its sources, but was not a direct adaptation of the work.
Answer: William Craig's 1973 nonfiction book