Writing the 'right' book?

There is a book catalogue that lands in our letter box occasionally. I first received someting else about twenty-five years ago. It was a new venture from somewhere that aimed to provide soft covered previews of non-fiction texts with an emphasis on subjects like language, linguistics, mathematics, physics etc.
Most of it was of little interest to me. I could not afford to buy the language and lingustics texts even at those prices and the mathematics and physics were way above my furry head. So were most of the other subjects.
Eventually the marketing experiment, if that is what it was, died out and it was replaced by a mainstream mail order company. Once in a while my father or I will order something from the catalogue. It will usually be something that is greatly reduced, a clear 'remainder'. Very occasionally it will be something that our local indie cannot, for some reason or another, access.
Most of the books however hold no interest whatsoever.
"Do people really want to read all this doom and gloom?" my father will ask, "Do they want to read about violence and sex abuse and child molestation? Why do they want to read about 'real life' mass murderers?"
Doom and gloom is what makes headlines in the media. There is very rarely a good news story in the headlines - unless it relates to winning something in sport. If the media is anything to go by then people seem to want to vicariously live doom and gloom. It makes them feel good. It has not happened to them.
And this gets translated into books written and published as well.
Now Nicola Morgan is saying it is simple. You have to write the 'right' book to get it published. I am pondering this. For many years the Royal Society for the Blind had, probably still has, a committee which decided which books would be made available as talking books. Their choice was often apparently paternalistic. Doom and gloom did not feature too highly on the list of available books. It was not what they wanted their clients to read and, if they are to be believed, not what their clients wanted to read.
There was also the child in the library who was clearly tired of doom and gloom and just wanted 'an ordinary adventure story'. Talking to other children made me realise that adults who are, after all, responsible for choosing what gets published for children are guilty of the same sort of sin as the RSB once was. They choose books they believe children should read rather than books children want to read. Yes, given the choice, some children will head for a constant diet of 'ice-cream' and they do need to have some vegetables thrown in. Many other children will read a wide and varied diet without too much encouragement. There is a limit to the number of 'greens' or 'social interest' books they can handle.
So, when an author writes the right book is it the right book for the publisher? Is it the right book for the parent or the teacher or the librarian? Is it the right book for the child? I suspect that the last matters less than it might because, if books are there, children will tend to read them in the absence of something better. Then they grow up wanting doom and gloom.