You Can't Be Serious is the no-holds-barred autobiography by one of sport's more enduring legends, John McEnroe. With a title taken from one of his regular memorable on-court tirades against errant umpires, McEnroe - 'Super Brat' or 'Mac the Mouth' as he was dubbed at the prime of his career as tennis' tantrum king - tells all on love, life and the tennis tour. He writes that he feels churlish about some of his bad-boy antics and admits the rage that fuelled most of them is still not quelled. The other part of the book - and the part most observers want to read - deals with his marriage to firebrand actress Tatum O'Neal. Never one to keep calm herself, O'Neal's pairing with McEnroe was seen at the time as a marriage made in tantrum hell. And that's how McEnroe describes it in his book, too. Unsurprisingly O'Neal, the precocious Oscar-winning daughter of Hollywood lothario Ryan, has not taken the accusations contained in the book on the chin. Now 38, she has forced her 43-year-old ex on to the media baseline with a series of equally vitriolic responses. And so, in a war of words the fiery pair have rekindled one of the sporting world's much-missed pastimes: Mac-watching. With end-to-end snipes, barbs and accusations, the exchange has all the excitement and passion of one of Mac's duels with arch-rivals such as Bjorn Borg, Ivan Lendl or Jimmy Connors. First serve: McEnroe calculatedly releases his book to coincide with Wimbledon, guaranteeing blanket coverage for the tome at a time when eyes and ears are on him anyway as NBC's controversial commentator for the tournament. Fifteen-love: with more than a hint of that spoilt-brat attitude that made him the most reviled if admired sportsman of his generation, in his book McEnroe calls O'Neal a lousy mother, a bitter person and a hopeless heroin addict (the latter O'Neal has already admitted). Thirty-love: soon after the book is published in Britain, under the abridged title Serious, O'Neal briefly speaks to the Daily Mail, telling the newspaper that McEnroe is a 'sociopath'. Thirty-fifteen: reviews of the book are none too glowing and McEnroe is deemed still lacking in charm. Also, the book's jacket, picturing McEnroe walking sullenly through Times Square, is derided as pretentious and the pose - burying his head into the collar of a black trench-coat - is lambasted as a poor attempt at replicating a famous James Dean portrait. Foot-fault. Thirty-all: McEnroe returns O'Neal's volley with a delicate, diplomatic response; relations between the two are 'very strained' he tells Time magazine. His magnanimity wins him some respite. Forty-thirty: O'Neal returns fire with a ferocious two-handed drive at McEnroe's sporting legacy as she spills all to television news doyen Barbara Walters on ABC TV's popular 20/20 show last Friday. In it she admits to Walters that she had indeed been strung out on drugs for much of the past decade, but that she had been clean for the past three months and was taking her life seriously. More importantly, she takes the opportunity to serve a few aces to McEnroe, accusing him of taking steroids while he was a professional player, becoming violent after taking the drugs and using cocaine and marijuana between tennis tours. Deuce; Advantage: O'Neal. There's little doubt this hate match will go on long after the excitement over the book has died down, especially as McEnroe was recently granted custody of their two children on the grounds that O'Neal's drugs problems made her unfit to care for them. But once the chalk dust has settled, there will only be one winner: publisher Putnam, which has already ordered another printing of the book to keep up with demand. You Can't Be Serious by John McEnroe with James Kaplan (Putnam $260). British edition also available: Serious (Little Brown $170).