If a reader were to judge a writer by his characters it would be reasonable, perhaps even sensible, to be wary of Herman Koch. The Dutch writer and sometime actor has created some of the vilest men that contemporary literature has seen since The Slap. Christian Tsolakis's notorious novel seems a natural touchstone for discussing Koch's work, in which patriarchs reveal a pathological pugnacity that borders on psychopathy, and the nuclear family implodes. In Koch's 2009 book The Dinner, the protagonist's depravity is slowly unmasked over a four-course meal at an upmarket restaurant. In his latest, Summer House With Swimming Pool, it is clear from the first sentence that the doctor narrator may need some medical attention himself.

It is a relief, then, to find that Koch is genial company and that he seems genuinely thrilled by his recent success. Koch has been writing for almost 30 years, so can be sanguine about his recent ascendancy from middlebrow writer with mediocre sales to celebrity author with a high-profile film deal under his belt and a legion of book clubs signing up to read his latest novel.

It all began with The Dinner, which was published in English in 2012. "I didn't expect that it would get so many readers, even in my own country," Koch says modestly. "I mean, I never had to complain when my books came out, because there were reviews in all the newspapers, and they achieved moderate sales: 10,000-20,000, maybe, which is not much but also not bad; they didn't end up in second-hand bookstores too quickly after publication. But outside of Holland I was unknown, and the book would be my debut, a first novel for most of the readers. So the success was a surprise."

Realising the significance of an English translation, however, was overwhelming. "It opens up everything for you as a writer," Koch says, "because so many people can read books in English. It is not just people in England, the US, Australia. I am Dutch, but I read mostly books in English. But from that first translation The Dinner is now translated to 37 languages, and that is a good feeling for a writer from a small country, writing in a minority language that nobody cares to learn. Now I have a bigger audience, yes, but it is also something different for you as a writer."

Distance in translation Koch never rereads his

books in Dutch. "I remember every mistake I made, every doubt about a certain sentence. But when I read The Dinner and Summer House With Swimming Pool in English, to check the translation, it was like reading a book by somebody else. It was very interesting. I thought, This isn't bad. This writer knows what he is doing. You never get that experience of distance in your own language."

In one very particular way, the success of The Dinner might indeed be considered surprising. Despite or perhaps because of its unpleasantness, it is a compulsive read. The story centres on a horrific crime committed by Paul, the narrator's son, but it opens up an important moral question of how far parents will go to defend the actions of their children.

The story was inspired by a real crime, but Koch ascribes the enormous interest in the book to the taboos of polite society. “I think people liked the fact that Paul says things that they would be afraid to,” he says. “He has thoughts that they don’t feel free to express or say aloud. For example, at home, I have a neighbour, a nasty man. One day I came back to the house and saw him all in casts. He had been run over by a car, and I said to my wife, ‘They just didn’t hit him hard enough.’ That’s the kind of thing that you can’t say too much, but you can say it in a book.”

There was always a risk, Koch admits, of alienating the reader. But he began from the same point that the reader does. “When I started writing it was a question for me, too: how far would I go along with the character? How far would he go?”

Summer House With Swimming Pool follows The Dinner in its exploration of uncomfortable truths. Its protagonist, Dr Marc Schlosser, is disillusioned with his job and his patients. "He has been too long in the profession," Koch says, "and is disappointed that there is not more status or prestige for what he is doing.

“His circle of patients is made of writers, actors, small celebrities, but in their company he is just someone who opens the bonnet of a car but can’t change anything essential. He is a GP, not a surgeon. All he can do is give them a prescription and listen to them and reassure them and tell them it is okay to drink a bottle of wine every night. They don’t really need him. The only thing they need is the illusion of his attention.” When Schlosser is accused of malpractice, however, he “must protect his children from a threat from outside”.

Koch is aware of the similar thrust of the books. “I was worried about repeating myself, that people would think I was just writing the same again. But they are about different moral choices, and I decided, yes, I must write this now.”

First person

In fact

The Dinner

and

Summer House With Swimming Pool

are part of a type of trilogy, the first volume of which,

Odessa Star

, was published in English in 2013. They are novels that centre on the family, and the compromises parents must make in consideration of their children’s needs.

They are also united by their use of compelling first-person narratives, a technique Koch honed during his brief life as an actor, writing and performing comic sketches for television.

“Thinking in the first person is what you do when you act,” Koch says. “If you know how somebody talks, the story is 90 per cent written. But I think that while it is more natural to write in the first person, it is also important to remember that a first-person narrator is a character, too. They can tell you a story, but you have to ask always, Is this the truth? Because the narrator might think they are in control of the story, but they are not. The reader always knows the character better than they know themselves.”

But the writer knows them, and their nasty predilections, best of all. Summer House With Swimming Pool is published by Atlantic Books