How to explain to the world that to remain young, his father drank the blood of newborn babies, cooked and ate their livers?

Nirip, in Upamanyu Chatterjee's latest novel Fairy Tales at Fifty, struggles against this and other "fairy" facts of his life, even as he obsesses about turning 50, his impotence and all other symptoms of mortality. His father, a businessman who has built a huge evil empire by selling skeletons and stealing kidneys, among other things, is an ogre who needs, in addition to the babies for dinner, an unending supply of young girls; his mother is a witch who reigns over lizards and parts of his father's empire; his half-sister, who would be a man, kills whoever annoys her slightly.

Meanwhile, Nirip's brother, Anguli - short for Angulimala, the man from the Buddhist story who made a garland out of the fingers he cut from the men he killed - is about to cross his path. Anguli, like his original, has been on a killing spree, but since he was a child. The twins were separated at birth. At one point in the story will begin a phantasmagoric descent into a kidnapping and an unusual cricket match.

Chatterjee's teeming world is full of monsters, murderers, serial killers, people spouting blood the way Nirip's fancy teapots spout expensive tea. More easily perhaps. It is not life at its nicest. It is a whirling, crazy, vicious, vile world from which recognisable human features have been effaced.

Are things really so bad? Even if they are funny? For, funny they are. One of his teapots reminds Nirip of a wet nurse he had; he has reserved the pot for brewing some of the world's finest teas, "which he drank, naturally, without milk".

"If you are looking for a philosophy, life is horrible," says Chatterjee calmly. The gentle and charming Chatterjee is most unlike the creatures he has unleashed on his readers. In Calcutta to attend the Kolkata Literature Festival 2015 at the Book Fair, he refers to the killing of the Jordanian pilot just a few days ago, to the casual violence that surrounds us. How else can you talk about a world in which a man is burnt in a cage like that?

Chatterjee says it is not as if something specific led to Fairy Tales, his sixth novel, the first being English August: An Indian Story (1988), which inspired a cult following. He suggests he would like to move forward from this story of "dislocation", of a young urban IAS officer posted in the small town of Madna, drowning himself in marijuana, masturbation and Marcus Aurelius, and talk about the other books as well.

"The germs of fiction have different sources," he says about his most recent novel. While the Nithari killings must have been on his mind -"it can't get ghastlier than that" - many other things got into the book to make it, to borrow a word used much in it, a "potent" brew. ("Petrified" is another word used frequently.)

"Many years ago I had read Mark Twain's The Prince and The Pauper. In one sense, I thought what a waste," says Chatterjee, a joint secretary at the Centre. He thought the poor kid's bit could be done better. He also borrowed Angulimala's story, little bits from Hindu mythology and also from the stock Bollywood story of the judwas (twins). "I wanted to take the cliches of fiction and transpose these into a typical modern narrative," he says.

In his earlier books, he has often continued with a story. English August led to The Mammaries of the Welfare State (2000), featuring Agastya, the IAS officer, again. But in Mammaries, Agastya remains much the same man, says Chatterjee. He wants to write a third book with him. The Last Burden (1993), Chatterjee's second novel, also had a sequel, Way to Go. Weight Loss is a stand-alone, "a comedy of sexual and spiritual degradation". He is also writing short stories.

Since his people are everyday Indians from all classes, speaking in everyday Indian languages, how is it writing in English about them? "If you are writing in English, inevitably you have distanced yourself from your subject matter," he says. "It encourages irony, comedy," he says. Sometimes such writing is peppered with gaalis to suggest "Indianness". "I let them (readers) know (the conversation is) going on in an Indian language."

Quite predictably, in Fairy Tales, grim ends wait for many - actually for all - of his characters. For "lives are precious only in fiction". Someone who has jumped down from the top of a building remains suspended in mid-air, though, "arms and legs flailing, still full of life in mid-air". But one person lives. "Someone has to live unhappily ever after."

Chatterjee is very happy with the end. Life is very grim indeed. But somewhere along the conversation he had also mentioned that he has a dog who laughs.