The Joke's Over, by Ralph Steadman

The faithful Sancho Panza to Hunter Thompson's Don Gonzo

In my mind, Ralph Steadman's spiky, grotesque drawings are primarily associated with the disturbing American landscapes of Hunter S Thompson's often psychotic gonzo journalism, in spite of Steadman's successful career of his own as a cartoon satirist. His memoir of Thompson, The Joke's Over, records neither his own, nor Thompson's life, in lurid detail, but rather the wildly erratic tempo of their bruising friendship.

Steadman first collided with Thompson when a flamboyant New York magazine called Scanlan's sent him to illustrate Thompson's coverage of the Kentucky Derby in 1970. This drunken binge ended when Thompson twice sprayed Steadman with Mace and ran him out of town as "a worthless faggot". So began a capricious liaison with this "elegant thug of a wordsmith".

Their second encounter - covering the America's Cup - ended with Steadman treated for substance abuse and severe hyperventilation. Hunter was at his best once the trip had become a catastrophe, Steadman admits.

Other notorious debacles followed: the 1974 Ali-Forman fight in Zaire, when Thompson sold their ringside seats, or their signal failure to catch a big fish in Hawaii in the 1980s. Thompson's gonzo style insisted that "the best fiction is far truer than journalism" and combined a loose approach to factual reportage with a visceral, cruel humour.

Steadman frequently felt the sting of this humour as Thompson, who emerges as childish, greedy and hugely egocentric, ridiculed his work.

Yet Steadman portrays himself as a "faithful Sancho Panza", always willing to illustrate Thompson's lunatic prose even if he was "too fucking nice" to hold out for a fairer cut. Thompson may have been a "wretched, cheating, lowdown sonofabitch" but, ultimately, Steadman seems willing to offset his shabby behaviour against the dubious assertion that "he wrote like an angel".

Steadman explains that Thompson "was much more into deals than personal affection". Possibly he was also depressive, long before the prospect of George W Bush's extended presidency catalysed Thompson's suicide in 2005.

The Joke's Over glosses the friction at the core of their friendship. "His bullshit was a wonderful aurora borealis of trepidation, failure [and] unnecessary hesitation," Steadman concludes. That is a fair and poignant assessment of the chaotic genius and messy legacy of Hunter S Thompson.