'Such a love between those two, why shouldn't it be?' Jaap Robben writes in 'Zomervacht' about a mentally disabled boy.

His parents worked in an institution for mentally handicapped people, so Jaap Robben spent many an hour as a child putting curlers into boxes. It formed the seed for his novel Summer coat. 'I wanted to write an exciting book with a disabled person as one of the main characters, because you hardly ever read about that world.'

Four years after his highly successful debut novel Birk Jaap Robben (34) is back with Summer coat, a wry and funny novel about a family with a scratch. Since his parents' divorce, 13-year-old Brian has been living in a caravan with his deadbeat father. Mother has Brian's severely mentally challenged brother Lucien under her care. But when she is travelling and Lucien has to be accommodated at home during the summer due to a renovation of the institution where he lives, Brian and his father take over the care. Needless to say, this causes problems.

Jaap Robben knows first-hand life in an institution, he says. 'When I was little, my parents worked at Piusoord in Tilburg, an institution for the mentally disabled. I often went along, as there wasn't much childcare in those days. So as a 2 or 3-year-old, I joined the day programme for the residents. Putting curlers in boxes, things like that. I liked it there, it was a special place.'

As a little boy, did you realise that people there were 'different'?

'Yes, definitely. There was a special closeness to the adult. An old granny I couldn't understand who wanted to show me her room. Or bears of guys who wanted to pet my stuffed animal. Funnily enough, I remember it all very well. Those curlers you had to put through a little machine and then - click-clack - the curler was in the sleeve. Someone said to me that I could do that so quickly and well, and it felt weird that I could do something better than an adult. Some people were so severely disabled that they were a bit scary, because they made crazy faces and were attached to their wheelchairs with all kinds of braces and a modified headrest like a helmet.'

Were you scared?

'Well, especially their shouting and unpredictability was exciting. The weird thing was that we never saw those people anywhere, only in that area with low buildings where they scurried around. In the supermarket, you never saw them. Only later did I begin to see the tragedy of that, the impact such a situation has on a family. In recent years, when I sometimes told someone what I was doing, it turned out that several friends had a disabled brother or a disabled sister, whereas I had never heard them talk about it.'

Was it an uncomfortable topic for them to talk about?

'No, usually it was because that sibling had died young or because they didn't really experience a brother-sister feeling. If a family member lives in an institution, he or she takes almost no part in your daily life.'

Why did you want to write about it?

'Because you never read about it. I wanted an exciting or intriguing book with a mentally disabled person as one of the main characters. Because if there is a mentally disabled person in a novel, it is almost always an extra. This has to do with the fact that people with a mental disability hardly ever develop, which is a problem for a main character. This is also why the perspective does not lie with Lucien, but with his healthy brother Brian, although Lucien does go through some development. There was a lot to figure out, because, for example, how can you find a language for someone who can hardly speak? I wanted you to understand this Lucien a bit by the end of the book; to get to know him through Brian and realise that there is a world behind Lucien's eyes.'

The infatuation between a healthy adolescent and a mentally disabled girl is on the ethical edge.

'Yes, it's a relationship that shouldn't be, but which you might start thinking for a moment: it would be quite nice for the characters. I was curious about where the line was drawn. What are her expectations, what his? When does such a calf love become abusive? Of many of the characters, the extent to which their intentions are good is just not entirely clear. I didn't have to do much for that. When a boy of 13 starts something with a mentally challenged girl of 19, you immediately think: that's not really possible. And if a 40-year-old man starts hanging out with a 13-year-old boy on a remote plot of land, it automatically raises the question of whether he is a paedophile. Then something doesn't even have to happen, the suspicion remains.

In this way, I wanted to play with the reader's expectations and prejudices. I also found it interesting to explore where my own morals lie. Such a love between those two, why shouldn't it be? And a boy like Lucien also has a dark side; how should you love such a boy? Is that even possible? My two-year-old son Midas now says 'auto-auto-auto' all the time. Cute, when you know that will soon be joined by the word 'bicycle'. It is developing. But imagine that he will soon be 14, with a beard in his throat, and he still only says 'auto-auto-auto'. Then you probably won't be able to hear it anymore.'

What do you hope readers pick up from it?

'I hope the book awakens empathy, sensitises people you might not otherwise look at. We all know the 'cuddly downies'. A lunchroom chain like Brownies and Downies mainly shows the light side. But you also have people with Down who are aggressive. In intellectual disabilities, there are all kinds of degrees, sometimes it has no name and it is also not clear what causes it. So what does daily life look like? Where is heaviness and where is lightness, where is happiness? The little boy Henkelmann, who lives with Lucien in the institution, is at first a repulsive boy; he bites himself. Yet I hope the reader will start thinking: oh, boy, how awful.

But since Birk I know people get so many different things out of it that I have no expectations or purpose. For myself, the only goal is that I want to explore those dilemmas. Because all sorts of things can be tested beforehand, having a disabled child almost becomes a choice and therefore, in some people's eyes, your own fault. I heard parents being told: you could have known and you chose to keep it, then you don't have to expect pity from us. So having a test is not just a choice, it is even almost a duty.'

The makeable life.

'Exactly. But who actually decides what a good life is? If someone says 'nah nah' when they mean drinking, is that a bad thing and should they learn to say 'drink' because that's just the accepted convention? Lucien also has moments of pleasure, for instance when he and Brian throw bottles in the bottle bank. Happiness and fine feelings are also in things we don't usually attribute them to.'