Mrkgnao! It's 16 June, which means it's Bloomsday, the day on which lovers the world over of James Joyce's 1922 modernist novel Ulysses get together to give thanks that they have this weird and wonderful book in their lives. No other novel is so controversial: you could divide lovers of the English-language novel into the people who think that the greatest one ever written is Middlemarch and the ones who think it's Moby-Dick, and those two groups would still get together and side against the people who think it's Ulysses. (The ones who think it's Pride and Prejudice consider themselves above such vulgar squabbling.)

Bloomsday first came about in 1954, when a bunch of dark-suited Irish literary men decided to hire a couple of horse-drawn cabs and spend 16 June following the route of events in the novel. It did not go as well as expected. Among the party were Patrick Kavanagh, a great poet but a man who never met an argument he didn't like, and Brian O'Nolan, better known as Flann O'Brien, who by this point in his career was a former comic genius in the process of drowning his talent in booze. By the time they reached Dublin city centre, drink and infighting had got the better of them.

Around the 1970s, Bloomsday was revived as an informal thing, finding a natural focus in locations like the James Joyce Tower and Museum, a converted Martello fort in Sandycove, south county Dublin, which is the location for the book's chapter and in which Joyce himself lived for less than a week. (Personal note: as a small boy, I used to play around the Joyce Tower, and not knowing any better I assumed that all famous writers had their own tower.) People would gather in places like the Tower and Davy Byrne's pub in Dublin's Duke Street, read from the book, give talks about it and if they happened to be near a catering outlet, eat food associated with it. One notable side-effect of this is the tendency of Dublin restaurants on Bloomsday to offer vast cooked breakfasts consisting of all the offal that the book's protagonist Leopold Bloom is said to enjoy: fried liver and kidneys, cod's roe, gizzards, stuffed heart, and giblet soup. In fact, Bloom is not a big eater: all he has for breakfast in the book is a pork kidney, a piece of bread and butter and a cup of tea. But that's memetic mutation for you.

Why do people do this? What's so great about this book that people feel compelled to gather together and share it with each other?

Most people these days probably encounter Ulysses as a set text in university. This is a pity, because one of the best ways to make any book seem difficult and boring is to make it a set text in university. The difficulty of Ulysses has been vastly overstated, especially by people who haven't read it, but let's be honest, it's not exactly Aliens Love Underpants; if you haven't read Joyce's earlier A Portrait of the Artist as a Young Man then you won't know where the book's other protagonist Stephen Dedalus is coming from, spiritually and intellectually speaking. And since Stephen has a chip on his shoulder roughly the size of the Siberian Federal District, and most readers probably don't have too strong a grip on the social and cultural climate of Ireland in 1904, the book can be hard to follow.

Yet it yields its rewards. Ulysses is usually talked about in terms of Joyce's ambition to be encyclopaedic in scope, or as if all it is is a tissue of references and allusions that you have to spot, but it also has a story. The story is told in lots of different styles, but it's basically very simple.

One morning in 1904 Dublin, a young intellectual named Stephen Dedalus decides that he's had enough of his roommates and his dead-end teaching job, and that he needs to make a new start, but doesn't know what or how. At the same time, across town, a Jewish ad salesman named Leopold Bloom sets off around town for a day's work, which involves a lot of running around after people and doing deals with them. He also attends a funeral, has lunch, and from time to time encounters various forms of casual anti-Semitism. Bloom has an ulterior motive for staying in town: he knows his wife Molly, a talented singer, is having a thing with her booking agent, and he'll be coming to the house for a shag that afternoon. Stephen and Bloom, who know each other by sight, keep nearly meeting, but never actually do so until the evening, when Bloom, out of compassion for a woman he knows who's in labour, goes to visit her in hospital and finds Stephen getting rat-arsed with a bunch of medical students. Bloom follows Stephen to the red-light district, where Stephen gets more drunk and things get trippy. Then Stephen gets thrown into the street, where he makes a few anti-colonialist snarks that attract the attention of two drunken British soldiers, one of whom knocks him down. At this point Bloom intervenes, and when things calm down Bloom takes Stephen for coffee, then home to his house for a cup of restoring cocoa and a chat. The two having made tentative friends, Stephen leaves. Bloom goes to bed, and his wife Molly sits up thinking about their marriage, deciding in the end that he's a good sort and maybe she'll stick with him after all.

Ulysses is a book about ordinariness. There is no great drama in it; unlike Middlemarch and Moby-Dick, it's a comedy. Early critics thought that when Joyce depicted Bloom's ill-informed thought processes about everything from Palestine to geometry, he was making some satirical point about how small Bloom is compared to the cunning Odysseus, but they failed to spot that Joyce is celebrating Bloom's intellectual curiosity, not mocking his ignorance. Oxford professor John Carey criticised the book on the grounds that Bloom himself would be unable to read it, apparently under the delusion that no one can hope to understand who hasn't studied it at college level. Yet its influence has reached far: legendary San Pedro punk band the Minutemen had an instrumental on their classic 1984 album Double Nickels on the Dime called 'June 16th', and the tune's writer, bassist Mike Watt, confirmed in an interview that the tune is named after Bloomsday, voicing his admiration for Joyce's attempt to write about 'everything': 'And in a way the Minutemen were trying to do the same. Never sat down and agreed to do this or anything, but it seems like we're trying to write about everything. The whole world, the history, the future, what can be, could be, would be, what might have been. […] basically, the things about one fucking day!'

That phrase 'basically, the things about one fucking day' pretty much sums up what Ulysses is about. Since the copyright on Joyce's work expired in 2011 (a great day for the Joyce industry), Ulysses is more available than ever. Do yourself a favour and give it a go; like all classics, it never gets old.