When a modern painting tops $20 million at auction, a certain Rubicon of fame and prestige has been crossed. On February 8 at Christie’s in London, “Study for Portrait II” (1956) by the British painter Francis Bacon (1909–1992) is expected to sell for about $23 million, a record for the artist. One of a series of Bacon works depicting somber popes on thrones, “Study for Portrait II” — which according to the Daily Tele graph belongs to Sophia Loren — will handily top the record $15 million paid last November for a later work by Ba con, “Version No. 2 of Lying Figure with Hypodermic Syringe” (1968) at Sotheby’s in New York. How did Bacon, who according to biographers – including a longtime friend and confidant, Michael Peppiatt – began as a homeless adolescent hustler with an interest in interior design, develop into one of the most prized painters of the modern era? Mr. Peppiatt, who has already authored a life of the artist, “Francis Bacon: Anatomy of an Enigma” (1997), offers further explanations in “Francis Bacon in the 1950s” (Yale University Press, 224 pages, $50).

This new book was written to accompany a traveling exhibit which, originating at the Sainsbury Centre for Visual Arts in Norwich, England, can be seen at the Milwaukee Art Museum until April 15, after which it goes to Buffalo’s Albright-Knox Art Gallery from May 5 to July 30. Born in Dublin to English parents, Bacon was thrown out of the family house by his homophobic father. In his teens, he advertised in London newspapers for work as a “gentleman’s companion” and found plentiful opportunities. A 1927 Paris gallery showing of Picasso’s drawings inspired him to be an artist, and after a couple of years in interior design, he began to paint abstractions based on the human form. By the end of World War II, with an image of a flayed animal carcass, “Painting” (1946), now in New York’s MoMA, Bacon had cemented his reputation as a creator of unsettlingly powerful and intense images of fleshly pain.

To support these works, and his habits of gambling and guzzling champagne, Bacon found a new patron in the British supermarket heir Robert Sainsbury (1907-2000), who with his wife Lisa began the collection today housed at the Sainsbury Centre for Visual Arts. Bacon’s portraits of the couple are uncompromisingly authentic spatial investigations with a hypnotic, ghostly presence. Bacon could be a courtier and yet remain himself, as Mr. Peppiatt recounts: The Sainsburys once drove Bacon home after a party, only to prevent him from cutting up one of his early pope paintings, which they added to their collection.

Apart from sponsors, in the 1950s Bacon also gathered a cast of friends and colleagues whom he would repeatedly portray on canvas. These included the painter Isabel Rawsthorne (1912–92), whom Bacon depicted in triptychs with wildly energetic facial angles as dynamic as a multilevel motorway. Another model was Peter Lacy, a former Royal Air Force fighter pilot whom Bacon met in a bar, beginning a lengthy sadomasochistic relationship. In 1962, Lacy committed suicide, as would Bacon’s next model and lover, George Dyer, a petty criminal whose affair with the artist inspired the 1998 British film “Love Is the Devil: Study for a Portrait of Francis Bacon” in which Dyer is played by Daniel Craig — now starring in a more famous S&M role, James Bond — and as Bacon, Sir Derek Jacobi. Bacon was clearly inspired and energized by the rugby-style physiques of his paramours, who brutally crouch, squat, and wrestle in his paintings. Allen Ginsberg, himself no discriminating arbiter of refined companionship, complained that Bacon, whom he met in Tangiers, painted “mad gorillas in grey hotel rooms.”

Now that these gorillas — as well as the rest of Bacon’s art — have turned to gold, detailed studies of his achievement are timely. Mr. Peppiatt knows his subject, but his prose can be overwrought: “Like a wound, we all carry within us an obsession with the period preceding the major events that mark our lives.” Mr. Peppiatt’s reading of Bacon’s works is sometimes facile, such as when he sees “Three Studies for a Crucifixion” (1962), now in the Guggenheim Museum, as direct autobiography, with Bacon himself supposedly shown being expelled from home, crucified, and flayed in the painting’s three panels.

Yet Bacon’s work is far more ambiguous than that. We cannot be sure that all of the popes with open mouths are in fact screaming, although some clearly are and a major modern symphonic work, Mark-Anthony Turnage’s “Three Screaming Popes” (1988-9) was inspired by Bacon’s coloratura pontiffs. Why Bacon chose to portray popes remains a mystery. Psychological theories which claim that the popes illustrate a paternal obsession are too reductive. Like Bacon’s notoriously messy London studio, now reconstructed precisely at the Dublin City Gallery, there are endless layers and superimpositions in this powerful artist’s work which remain elusive, even after books like this.

Mr. Ivry last wrote in these pages on “Family Pictures,” an upcoming exhibition at the Guggenheim Museum.