James Carroll Booker III was born in New Orleans on December 17, 1939, the son of Ora Cheatham Booker and the Rev. James Harald Booker, a Baptist pastor. His father and grandfather were both ministers and both played piano. Known as J.C. in childhood, he was trained as a classical pianist from the age of six and played organ in his father's churches. By eleven he was playing blues and gospel organ every Sunday on the New Orleans radio station WMRY, and by twelve he had learned all of Bach's Inventions and Sinfonias. By his own account he was struck by an ambulance at nine and broke his leg in eight places; he later traced his addiction to the morphine he was given, and the injury left him with a permanent limp. At school he befriended Art Neville, Charles Neville and Allen Toussaint. From 1953 he attended Xavier University Preparatory School, where the band director was Ellis Marsalis Jr., who noticed how advanced his Bach playing was. He graduated in 1957.

He made his first record at fourteen: "Doin' the Hambone" and "Thinkin' 'Bout My Baby," cut for Imperial in 1954 under the name Little Booker and produced by Dave Bartholomew. The single did not sell, but Bartholomew then used him as a ghost pianist behind Fats Domino, a pairing that returned in the late 1960s. Through the late 1950s and early 1960s he worked in New Orleans rhythm and blues and blues bands. He toured with Huey "Piano" Smith and covered for Smith on the road, played with Shirley and Lee and with Joe Tex, and recorded piano in Houston with the bluesman Larry Davis between 1958 and 1960, in Chicago with Junior Parker in January 1960, and in New Orleans with Bartholomew's studio band, Earl King and Smiley Lewis. He played organ on a Lloyd Price session in 1963. In 1958 he played for the visiting concert pianist Arthur Rubinstein, who was reported to have said he could never play that fast.

His one national hit was an organ instrumental. "Gonzo," issued on Peacock in 1960 and backed with "Cool Turkey," reached No. 43 on the Billboard pop chart and No. 3 on the R&B chart in the week of December 5, 1960. It was the best known of a run of Peacock organ singles that also included "Smacksie," "Tubby" and "Cross My Heart." That fall he enrolled in the music department at Southern University but did not stay beyond the first semester.

The mid-1960s brought a string of losses. He lost his sister in September 1966 and his mother in June 1967, and within weeks of his mother's death he was arrested outside the Dew Drop Inn for heroin possession. He served a one-year sentence at Angola prison, where he lost his left eye in an assault. His run-ins with the law brought him into contact with the district attorney Harry Connick Sr., and the arrangement that followed had Booker giving piano lessons to the DA's young son, Harry Connick Jr.. After his release in 1968 he went back to session work, recording with Fats Domino in New Orleans and, in July 1968, cutting tracks in New York with Freddie King that came out in 1969 and 1970. He is credited on keyboards on King's Freddie King Is a Blues Master (1969) and on piano on a 1969 Columbia collection of Aretha Franklin recordings, Today I Sing the Blues.

He came back to prominence in the 1970s. In 1973 he recorded an album at Paramount Studios in Hollywood with members of Dr. John's band; the master tapes went missing from the studio library, a copy of the mixes surfaced in 1992, and the music was finally issued in 1995 as The Lost Paramount Tapes. In 1974 he played organ in Dr. John's Bonnaroo Revue touring band, and through the middle of the decade he appeared as a sideman on records by Ringo Starr, John Mayall, the Doobie Brothers, LaBelle, Maria Muldaur and Geoff Muldaur. His set at the 1975 New Orleans Jazz and Heritage Festival won him a contract with Island Records, and Junco Partner (1976), produced by Joe Boyd, was the result. In January 1976 he briefly joined the Jerry Garcia Band for two shows in Palo Alto, California.

Europe gave him the respect he felt he lacked at home. His Hamburg concerts of October 29 and 30, 1976 were recorded and released as The Piano Prince from New Orleans. He was recorded in Manchester in October 1977, and at the Boogie-Woogie and Ragtime Piano Contest in Zürich on November 27, 1977; the Zürich set, issued in the United States as New Orleans Piano Wizard: Live!, won the Grand Prix du Disque. He played the Nice and Montreux jazz festivals in 1978, recorded a session for the BBC, and made a Leipzig recording, Let's Make a Better World!, that became the last record produced in East Germany.

Back in New Orleans he was the house pianist at the Maple Leaf Bar in the Carrollton neighborhood from 1978 to 1982. John Parsons recorded him there on cassette, more than sixty hours between 1977 and 1982, and the best of it was issued on Rounder in 1993 as Spiders on the Keys and Resurrection of the Bayou Maharajah. His last studio album, Classified, was recorded October 18 to 20, 1982, at Ultrasonic Studios in New Orleans with the bassist James Singleton, the drummer Johnny Vidacovich and the tenor saxophonist Alvin "Red" Tyler. By then his health had badly declined. The filmmaker Jim Gabour recorded his final concert at the end of October 1983. James Booker passed away on November 8, 1983, at the age of 43, in a wheelchair in the emergency room of Charity Hospital in New Orleans, waiting to be seen. The coroner's certificate gave the cause as renal failure related to chronic heroin and alcohol use.

His reputation has grown steadily since. Harry Connick Jr. and Henry Butler have recorded pieces that pay tribute to him, a tribute album of his songs by various pianists, Patchwork, appeared in 2003, and Joshua Paxton's transcriptions of his solos have been published by Hal Leonard. Lily Keber's documentary Bayou Maharajah: The Tragic Genius of James Booker premiered at South by Southwest on March 14, 2013, and Rounder issued an expanded edition of Classified that year.

Booker is a New Orleans rhythm and blues pianist first, and that is where his records and his one chart hit sit, so this is a crossover profile. English Wikipedia opens by calling him a New Orleans rhythm and blues keyboardist and singer, and AllMusic's style tags for him are New Orleans blues, boogie-woogie, piano blues and New Orleans R&B. The jazz side is real and documented all the same. AllMusic lists jazz among his genres and says his left hand fused the jazz and rhythm and blues idioms of New Orleans with a good deal of gospel; he played the Nice and Montreux jazz festivals in 1978; and his repertoire ran from "Tico-Tico," "On the Sunny Side of the Street," "Come Rain or Come Shine" and "Angel Eyes" to the Beatles' "Eleanor Rigby," Roger Miller's "King of the Road," and Chopin and Rachmaninoff. He memorized solos by Erroll Garner and Liberace, took elements of his keyboard style from Tuts Washington and Edward Frank, and listened closely to Professor Longhair and Ray Charles.

The sound that tied this together was a rolling backbeat figure in the left hand, close to Fats Domino's feel and often called the Booker groove, over which he stretched a tune into a medley of itself, slipping in classical quotations, phrases from other songs and long improvised runs. Allen Toussaint praised the complexity under the groove, and the transcriber Joshua Paxton has described the effect as Ray Charles with Chopin's technique. His singing was plaintive and exposed, as comfortable with a gospel hymn as with a standard. He was openly gay and performed in capes and costumes. Much of his best-loved work is live, from the Hamburg and Zürich concerts to the Maple Leaf Bar tapes.