Avenger by Frederick Forsyth<br></br>The Teeth of the Tiger by Tom Clancy<br></br>Empire State by Henry Porter

Spy-thriller chiefs know they must penetrate the shadowy new world of international terror. Two veterans botch the job, reports Bill Greenwell, but a younger contender succeeds triumphantly

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Frederick Forsyth's tenth novel, Avenger, has it all: clumsy dialogue, dodgy sentence structure, global violence, ponderous and boring editorials, crude paragraphs, a central character with the charisma of a midge and, worst of all, GCSE lectures in contemporary politics and the philosophy of counter-terrorism. At one point, a character sighs on our behalf. What he is hearing is "becoming tiresome and had long been pointless". He turns on another character and says, "Spare me the history lesson."

Is this a momentary piece of Forsythian irony? It seems unlikely. We are treated to quick disquisitions on Vietnam, Nazi Germany, Cambodia, Yugoslavia, Panama, the Achille Lauro, the Gulf Wars and al Qa'ida. If I were one of the Tunnel Rats to whom this hokum is dedicated ("You guys did something I could never force myself to do"), I would be turning in my stomach.

The Tunnel Rats were an élite who fought a dirty war against the Viet Cong. Our hero, Cal Dexter, has been one of them. He is now a solo mercenary who takes on impossible missions, in this case to nobble a Serbian bastard holed up in "San Martin", the fictitious "former Spanish Guyana". The Serb's hideaway is surrounded by sharks, piranhas, Dobermanns, a South African security chief, men with guns, cameras, computers, etc. The US wants the Serb to lead them to the greater evil, USB (Usama bin Laden, not Universal Serial Bus).

Somewhere in this spirited tosh there is a thriller wriggling to get out. Towards the end, it is mindlessly exciting, although you would not wish the action on Pierce Brosnan. You wouldn't wish it on George Lazenby, come to that.

I went back and looked again at The Odessa File and The Day of The Jackal: still very readable. Forsyth's instincts for plot are now, however, submerged by his dull desire to trot through facts, figures and dates.

Tom Clancy's 13th thriller, The Teeth of The Tiger, moves the spotlight from his familiar hero, Jack Ryan, to Jack Ryan junior. His Ryan chronicles, which move backwards and forwards in time, have previously featured Jack Ryan's father. This one, however, is the most "recent" in both senses.

Junior is recruited by "The Campus", an invisible intelligence outfit which does what the CIA and FBI can't do: it assassinates global terrorists. In fact, it is rather like UNCLE, which Clancy twice tries to deny. He constantly reminds us that real spying isn't like the movies, especially Bond movies - but (oops) has the Campus chief happily fantasise that "this is what it must have been like to be 'M'".

Where Forsyth tells you "This is what I know," Clancy tells you "This is what I have researched." For instance, an injection of succinylcholine will kill, but will make the corpse indistinguishable from a heart-attack victim. A MAC-10 sub-machine gun generally has a poor finish on the metal. If you're trailing someone, wear a reversible jacket. For all this, Hereford isn't in Wales, and Mr Spock wasn't a commander.

The Teeth of The Tiger, like Avenger, is about international terrorism and likes history lessons too (the Kennedys "had a hard-on for doing Castro"). There is some cod philosophy: "The one thing that never changed in the world was human nature. The cruel and the brutal still existed." The characters mull over Big Ideas, and Clancy has a shot at avoiding racial stereotyping. But when it comes to the action, the assassins are "whacking" the "ragheads".

Clancy is writing for a post-September 11 audience: there are two quiet references. Here he has a mild problem since, in a previous novel, a Japanese airliner crashed into the Capitol and wiped out Congress (Jack Ryan subsequently becoming president, a role from which he has since retired). In The Teeth of The Tiger, Islamic terrorists use Colombian gunrunners to get into small-town America, in order to attack four shopping malls. By outrageous coincidence, the other two Campus recruits, Junior's twin cousins Dominic and Brian Caruso (FBI and Marines respectively), are shoe-shopping when one team starts firing.

Clancy likes writing about killing, and he is very bad at it. This novel is also crammed with woefully turgid dialogue and stylistic irritants (does anyone "avail" themselves of coffee?). The plot is protracted and tedious; as with Forsyth, one harks back to better efforts like Clancy's Clear and Present Danger. And would three undercover agents ever really be relatives of an ex-president? No need to encrypt your answer.

Henry Porter's third thriller, however, is a wonderful treat. Empire State does as Forsyth and Clancy know they must: plug us into internet esponiage, international security- service hacking, and the pursuit of al Qa'ida. But the characterisation is generous and the control of the plot is superb.

Robert Harland, the UN agent of Porter's equally brilliant A Spy's Life, makes a welcome return. A new heroine, Isis Herrick, is pleasingly testy and convincing. She is an MI6 agent in her thirties who has the instincts of a great detective (for what is a spy novel if not fancy detective fiction?). Herrick's ability to link apparently random pieces of information keeps the reader thoroughly entertained.

The novel starts us in two places: at Heathrow, where an American presidential envoy is entering Britain under an assumed name; and on the Albanian border, where a weary Muslim fighter is returning the hard way from Afghanistan. Porter uses these jumping-off points to create sparkling interstices, stories within stories, triple-bluffs. Above all, he maintains a perfect uncertainty about where events will take us, and which of his competing secret services (British, American, Israeli, UN) are completely on the ball.

Occasionally, the characters discuss morality, which they don't need to do. But this is essentially a novel which burgles your imagination, plays some light havoc with it, and returns it to you in even better shape. Porter is neither bossy (like Forsyth), nor crass and slapdash (like Clancy). His landscapes, language and action are intriguing. Here is a spy writer whose work is becoming increasingly unbeatable.