"[1] Sullivan has written for a number of nationally recognized publications, including Esquire; The Washington Post; The Guardian; Rolling Stone; and Wired.

Although, the mini-series was nominated for two Golden Globe[5] awards and four Emmys,[6] it was considered "factually inaccurate" and did not stay true to the source material.

[2] In 1996 Sullivan published The Price of Experience: Money, Power, Image, and Murder in Los Angeles, his long-awaited book about the Billionaire Boys Club.

[2][17][18] In 2002, Sullivan published LAbyrinth: A Detective Investigates the Murders of Tupac Shakur and Notorious B.I.G., the Implication of Death Row Records' Suge Knight, and the Origins of the Los Angeles Police Scandal.

[21] Eric Boehlert, a former senior writer at Salon, argued that too much evidence was based on Poole's oral testimony, and that Sullivan's timeline of the events didn't matchup entirely.

[31] City of Lies, starring Johnny Depp and Forest Whitaker, was scheduled to be released in September 2018 but was later pushed back.

[32][33] In 2019, Sullivan publish a follow-up book titled Dead Wrong: The Continuing Story of City of Lies, Corruption and Cover-Up in the Notorious B.I.G.

In April 2004, Sullivan publishedThe Miracle Detective, his book about his investigation into the apparition of 'Our Lady of Medjugorje' which is claimed to have appeared before six children in Medjugorgje, Bosnia, in 1981.

[34] His book was not only an investigation into the history of the apparition—and how other villagers and visitors since, have had similar visions at Medjugorgje—but also about his personal experience there, where he claims he experienced a miracle.

The book was met with some controversy,[40][41] mainly because Sullivan argued that Jackson was not a "child molester" and rather, that he was "pre-sexual" having never engaged in sexual intercourse at all.

[20] For most of his life Sullivan identified as an atheist, but in 1995 he underwent a spiritual conversion to Catholicism while he was in Medjugorje reporting on the Bosnian War.