When The Brothers Lionheart was published in the autumn of 1973, Astrid Lindgren was 66 years old and retired from her work as a children's book publisher. By then, she had written most of her most beloved books. Pippi Longstocking, The Children of Noisy Village, Emil in Lönneberga, Karlsson on the Roof, Lotta on Troublemaker Street, Mio, My Son, and Madicken were all publish,ed, translated, and loved worldwide. Only Ronja the Robber's Daughter came later, not until 1981.

The early 1970s were politically dominated by the Vietnam War, the Cold War, and independence struggles in several former colonies in Africa. The novel's theme of resistance against tyrannical oppressors was thus contemporary. However, the storytelling form was by no means contemporary. Strong leftist winds characterized the view of culture in general and children's literature in particular. Children's books were supposed to educate young readers about society's injustices, socialize them, and prepare them for the fight against imperialist and capitalist exploitation. Therefore, children's books were expected to be realistic portrayals of societal problems.

In this political climate, Astrid Lindgren wrote an adventure novel, a romantic and timeless tale about the struggle between good and evil, about courage and fear, love and death. And she did so without regard for consequences; several critics argued that the book was apolitical or politically simplified. They claimed that the story was not realistic and did not explain the structures behind evil and oppression. It was not the first time Astrid Lindgren had faced such criticism from a leftist perspective, and she had previously mocked the political anxiety prevailing in the children's cultural world on several occasions.

"Take a divorced mom, preferably a plumber, but an atomic physicist would do just fine as well, as long as she's not 'sewing' or 'nice.' Mix the plumber-mom with a few parts of dirty water and a few parts of air pollution, a couple of parts of world hunger and a few parts of parental oppression and teacher terror; add a couple of lumps of racial conflict and a couple of lumps of gender discrimination, then sprinkle generously with intercourse and drugs, and you have a strong and good stew."

From "A Little Conversation with a Future Children's Book Author" (1970)

Her belief was that children's book authors should be free, as free as any other author.

"I wish you and all other children's book authors freedom, the freedom that an adult author naturally has, to write about whatever they want however they want. If you want to write a shocking book for children about how difficult and impossible it is to be a human being in our world, you should have the right to do so. If you want to write about racial oppression and class struggle, you should have the right to do so. And if you just want to write a poem about a blooming island in the arms of the archipelago, you should actually have the right to do so without necessarily having to think, 'What rhyming words are there for dirt water and oil spills now?' In short: freedom! Because without freedom, the flower of poetry withers wherever it grows."

From "A Little Conversation with a Future Children's Book Author" (1970)

But The Brothers Lionheart did not only receive criticism with political implications. The major hesitation among adult readers concerned the natural and straightforward portrayal of death, especially the ending upset many readers. It was considered too dark and frightening. Some even argued that it encouraged children to commit suicide. Astrid Lindgren herself struggled with the ending of the novel. For the first time in her writing life, she had difficulty writing the final chapters. She carried the manuscript with her between various stops on her summer vacation in 1973, and it wasn't until July 31st that she finally concluded the story.

The children who read the book seemed to interpret it in a completely different way than the adults. Astrid Lindgren received thousands of letters from young readers thanking her, feeling comforted, and wondering about Skorpan and Jonatan in Nangilima. And, for the first and last time in her writing life, Astrid Lindgren sat down and wrote a letter to all the children who wondered. The letter, in which she told them what happened next, was published in Expressen in 1974.

None of Astrid Lindgren's books have been read in so many different ways. This is how she herself wrote about different interpretations of The Brothers Lionheart:

"If I were to ask an adult reader, 'What is this book about?' I might get the answer: 'It's about death and reincarnation and all sorts of horrible and sad things.' No child would ever respond like that. They read Lionheart as an exciting adventure book about two brothers who care extraordinarily much for each other and who are happy as long as they can be together wherever they go. And the children write to me and thank me for the happy ending.

But what about me, then, how do I read the book? Since I have so much childishness in me, as I do, I can read it as a child, and then I think, 'Thank goodness Skorpan found Jonatan in Nangijala and that they managed to escape all the horrors and that they arrived together in Nangilima, they surely had a good life there.' But then there's an adult part of me that thinks like this: Maybe it was so that Skorpan, lying sick at home in his kitchen, couldn't bear to live without Jonatan, when Jonatan had died, maybe he had to escape to his imagination and, as consolation, invent all the adventures in Nangijala, maybe he didn't die until the very last page of the book, and then not in Nangijala but at home in his poor kitchen on earth. But when I read a children's book, I prefer to be a child - that's why I'd rather not believe in my adult interpretation."

From "A Book Can Be Read in Many Ways"

Sources: Jens Andersen: "Astrid Lindgren, the Woman behind Pippi Longstocking" (Yale University Press 2018), Astrid Lindgren: "Det gränslösaste äventyret" (Eriksson & Lindgren, 2007), Lena Törnqvist: "Man tar vanliga ord" (Salikon förlag, 2015).

Behind the Iron Curtain, in Czechoslovakia, The Brothers Lionheart was controversial for reasons other than its portrayal of death. The book was not allowed to be published until 1992, after the Velvet Revolution when a non-communist regime took over. However, as early as 1981, the book had been smuggled in, translated, and circulated in so-called samizdat editions. Books were hand-bound on thin, typewritten paper sheets and distributed as underground literature. One such handmade copy is held at the Royal Library in Stockholm.