Comedy, PG Wodehouse reportedly once said, is "the kindly contemplation of the incongruous".

That is certainly true of Wodehouse's own work, which pokes fun at the mores of the English upper classes in a manner that makes it difficult to take offence and which is as immune to the ravages of time as fairy tales. Where his humour sprang from is no easier to pinpoint than the source of the Mississippi. Wodehouse, it seems, was born to make us laugh as Vladimir Putin was to have us rage. His genius - not a word we should use lightly - was in his ability to see the funny side of everything, even the Holocaust. Recalling his internment during WWII in a former Polish lunatic camp, he wrote: "Tost is no beauty spot. It lies in the heart of sugar-beet country....There is a flat dullness about the countryside which has led many a visitor to say, 'If this is Upper Silesia, what must Lower Silesia be like?'"

Silliness, of course, is in the DNA of all the great comic writers, from Shakespeare to Mark Twain, James Thurber to Sue Townsend. All of them, Wodehouse included, were premier league fantasists, inhabiting a parallel universe in which laughter was the one currency which could not be devalued. Wodehouse, one could convincingly argue, never grew up and remained for all his 93 years essentially the kind of schoolboy who is always cracking jokes and playing pranks. His alma mater was Dulwich College, which Raymond Chandler also attended a few years later. Its history was long and its ethos was sporting which Wodehouse embraced with a fanaticism bordering on addiction. Sex, however, did not consume him and romance was simply a springboard for farce. Animals, it seems, and pigs in particular, the fatter the better, interested him more than women. By and large, his was a contented existence, albeit one in which he worked like a ravenous waif in a Victorian sweatshop.

This is nowhere more evident than in the 99 books which comprise The Everyman Wodehouse, which began in 2000 and which is now completed with the publication of Louder and Funnier, The Prince and Betty and Sunset at Blandings. These three titles are not vintage Wodehouse and there is a sense of barrels being scraped and drawers being emptied. Having said that, Wodehouse was always capable of turning leftovers into something tasty. In Louder and Funnier, for instance, he offers a series of comic essays, a form which has all but disappeared from the literary landscape. In one, he fears for the future of authorship, as his peers desert Blighty for Hollywood's big bucks. In another, he calls for playgoers to have their own union, like actors and electricians. In yet another, he looks forward to the tennis at Wambledon, having misread an Editor's commissioning letter. "I suppose," he concludes, "I ought to write this article all over again", which perhaps he ought to have done.

The Prince and Betty is a romcom converted into a novel. It is the kind of thing Wodehouse could write in his sleep, which he may well have done. First published in 1912, when he was 31, it was heavily influenced by Anthony Hope's bestseller, The Prisoner of Zenda. Never afraid to pillage his own material, he lifted the plot from Psmith Journalist, one of his best novels. The eponymous Betty is a high-minded girl who abandons her beloved when he becomes involved in a Monte Carlo casino. Torn between passion and principle, Betty turns to poetry. "The great love-poems of the world, when she read them, had always left her with the feeling that their authors were of different clay from herself and had no common meeting-ground with her." A couple of decades later, Wodehouse had no qualms about plundering the plundered, ripping off The Prince and Betty in a novella entitled A Prince for Hire, the serial rights to which he sold to a magazine.

If this implies that he was a mercenary then so what? When inspiration didn't strike he sought solace in his previous output. Like most professional writers, he was a slave to routine. In the 1920s, recollects NTP Murphy, in one of several trainspotterish afterwords to Sunset at Blandings, Wodehouse liked to write in the mornings, walk in the afternoons before returning to his desk for a couple of hours in the evening. More often than not, his walk took the same path, which has allowed Murphy to identify the pig he believes was the model for the Empress of Blandings. Having said that, he cautions: "I do not claim for one moment that this was the only pig Wodehouse knew in his long life."

The manuscript of Sunset at Blandings was found far from complete at the author's bedside after his death. It is obviously a valedictory novel with many well-loved characters returning to the stage for a last hurrah. The supplementary notes are perhaps of more interest than the published draft which, had Wodehouse survived, would surely have been much revised. In his preparatory notes we see him teasing out the plot and adding flesh to the bones of the players. It is left to other Wodehouse scholars, Richard Usborne and Tony Ring, to speculate how the novel might have ended. Not the least problem is Lord Emsworth, who cannot be told anything lest he blurt it out. I know how he feels.

Louder and Funnier, The Prince and Betty, and Sunset at Blandings are published by Everyman at £10.99