Roald Dahl, born on September 13, 1916, was not a particularly nice person. Judging from the many available biographies, he was quite a nasty person. Yet readers, especially young readers, do not necessarily care about the person behind their favourite books. Most likely, they have their own picture of the author: warm, witty, a great friend of children and a great scoffer of conceited grown-ups.

Dahl is one of those many writers who are significantly more famous for their children's books than their works for a general (that is, adult) audience. Although his short stories are truly brilliant, he would hardly be hailed exclusively for them among the “50 greatest British writers since 1945” (The Times, 5 January 2008). The fact that this canon includes a number of children's writers (beside Dahl, C S Lewis, Philippa Pearce, Allan Garner, Philip Pullman and Rosemary Sutcliff) is remarkable in itself; it demonstrates that children's literature cannot any longer be dismissed as second-rate; and I would argue that Roald Dahl has contributed substantially to this recognition, repeatedly mentioned as the best-loved, best-selling author without the, regrettably, still derogatory appellation “children's”.

Yet for a long time, since the appearance of James and the Giant Peach, celebrating its fiftieth anniversary this year, Dahl's reputation as a children's writer has been ambivalent. Exceptionally popular for a pre-Harry Potter era, he used to be looked down at by teachers and critics, precisely because he was unquestionably loved by the young audience. The idea that popularity with readers is a sign of poor quality goes back to the elitist view of literature and arts. It is further amplified by the recurrent belief that children's literature should be edifying. Children's books that are enjoyable cannot be good for children, the argument goes. Children should gain knowledge from literature; learn lessons and morals. Giant peaches and talking insects contradict the laws of nature. Children who are cleverer than adults are abominable.

Although some of these reasons may seem obsolete (unfortunately, they are still around), Dahl's children's books have been subjected to hard critical scrutiny, especially the imperialist, racist portrayal of the tiny oompa-loompas in Charlie and the Chocolate Factory. It is easy to find ideological and aesthetic faults with Charlie and every other book by Dahl, but I am prepared to forgive them all for what is the primary thrust in Dahl's work, his belief in the competent, omnipotent child.

Dahl is irresistibly attractive for young readers because he allows his child protagonists to be unconditionally superior to adults. He is disturbing for adult gatekeepers for exactly the same reason. In our society, children are inescapably disempowered: they lack economic resources, political voice, social status, and must in every situation submit to rules imposed on them by adults. As adults, we are not too eager to cede our power. We don't even want children to get a glimpse of what it might feel for them to be empowered. Even the best children's writers frequently strip their characters of the power they had temporarily gained, with adults' approval, through their adventures. Dahl does not eschew children's ultimate ascent, even if it implies his own self-denial. Some of the cynicism of his adult production leaks into his children's books, and re-reading them as adults we wince.

Dahl offers his young readers what they want, a practice that even some of his most eminent colleagues within children's literature have condemned. He leads a poor hungry boy into a gastronomic utopia, much like the traditional folktale hero winning a princess and a kingdom in hard competition with less virtuous candidates. Adult critics who point out that excessive chocolate eating is bad for your health have missed the point. The recent film adaptation that shifts the focus from Charlie onto Willy Wonka (played by Johnny Depp) and his deprived childhood, goes against the very spirit of the original. It is not about a child gaining a paradise; it's about a frustrated, infantile adult buying affection from a gullible family. Luckily, Dahl didn't live to see his great story distorted.

The most enigmatic aspect of Dahl's books is their sustainability. Several generations of readers all over the world have grown up with James, Charlie, Danny, Matilda, Sophie and the Revolting Rhymes. As the first readers grew up and became teachers, librarians, critics, policy-makers, parents and grandparents, Dahl is suddenly no longer a danger to the order of the world. Looking back to our childhood reading, we rational adults occasionally remember how it felt to be empowered together with our favourite characters; what is was like to laugh with them and to laugh at their adult adversaries. Dahl has burst generational as well as national boundaries. We share him with our children and with our friends abroad. This is what we celebrate on Roald Dahl's birthday, the 13th of September.

Maria Nikolajeva is a Professor of Education and a the Director of the Cambridge-Homerton Research and Teaching Centre for children's literature. Her most recent book is Power, Voice and Subjectivity in Literature for Young Readers (Routledge, 2010)