In October 1943, shortly before her deportation, the young German Jewish artist Charlotte Salomon gave Life? or Theatre? – her monumental series of semi-autobiographical artworks – to a friend for safekeeping. Upon arrival at Auschwitz, aged 26, newly married and pregnant, Salomon was murdered, and it would be many years before Life? or Theatre? would be exhibited.

Subtitled Ein Singspiel, a play with music, the work comprises over 700 multilayered gouaches, many with transparent textual overlays. It is considered by some people to be the first graphic novel. Painted between 1940 and 1942, Life? or Theatre? combines historical events and personal memories, referencing film, music and theatre. It tells the story of a traumatic past and a troubled family marked by the suicides of more than one of Salomon’s female relatives, including her mother. There are also hints of sexual abuse, a possible murder committed by her, and accounts of unrequited love. But throughout, there is a conscious blurring of reality and fantasy, with characters presented as fictionalised versions of significant and influential people in Salomon’s life.

Her tragic life and legacy has inspired numerous books and films, an opera – and now an animated biopic, Charlotte, which premieres at the UK Jewish film festival in London today before going on general release. Directed by Tahir Rana and Éric Warin, Charlotte features the voices of a starry British cast led by Keira Knightley in the title role and including Jim Broadbent, Brenda Blethyn, Mark Strong, Eddie Marsan, Sophie Okonedo and the late Helen McCrory in her final film.

So why does Salomon continue to fascinate, decades after her death? “It’s the combination of her overlooked genius and the compelling universal nature of her struggles,” Julia Rosenberg, the film’s co-producer, tells me from her Toronto home. Rosenberg received a copy of Life? or Theatre? as a bat mitzvah present many years ago and was drawn to Salomon’s story. “Perhaps I over-identified with Charlotte and her work as an alienated teenager and coming from a Holocaust family. But the similarities were not literal. It helped me think about feelings I had about myself that I couldn’t quite define, feelings I had about intergenerational trauma.”

Although Rosenberg had previously only made live-action films, animation seemed essential for this story. “Charlotte drew her life story, so I knew I needed to produce a drawn version of it,” she says. The film evokes the artist’s bold, expressive style, enhanced by a strong use of colour: dark interior scenes and rain-soaked Berlin streets contrast with verdant southern French gardens suffused with brilliant yellow light. The additional use of vivid recreations of Salomon’s paintings connects to “how we felt Salomon was feeling at given moments” Rosenberg explains.

Charlotte broadly follows the Berlin-born artist’s life, from her attendance at the city’s prestigious arts academy – curtailed due to growing antisemitism – to her leaving Germany for exile in the south of France, where she joined her maternal grandparents. It was here that Salomon’s grandmother took her own life, and also where she learned that the cause of her mother’s death was not flu, as she had always been told, but also suicide.

Along with her grandfather, Salomon was interned in Gurs detention camp and, some time after their release, while in hiding, embarked on Life? or Theatre? She worked in a terrified and depressed state, both as a Jew living in Nazi Europe and from fear that she was genetically prone to mental illness. The artwork is an investigation, believes art historian Griselda Pollock, who wrote Charlotte Salomon and the Theatre of Memory. “The project is not autobiographical,” says Pollock. “She undertook it to ask herself, ‘Do I live, or do I die?’”

As Salomon’s life and art were almost inextricably related, says the film’s co-writer David Bezmozgis, factual accuracy was important. “The only scene that we completely invented – but based on credible supposition – is her visit to the Degenerate Art exhibition in 1937,” adds Rosenberg. “It’s still the most attended art show in the 20th century and, as she was an art student in Berlin, we assumed she would have attended.”

Charlotte does not shy away from controversy and shows Salomon poisoning her grandfather, despite official records stating that he died from a head injury after collapsing in the street. Even though it is open to debate, there is enough primary and secondary evidence, such as a confessional letter written by Salomon, which was discovered and made public in 2015, explains Bezmozgis.

“When we started the film, there wasn’t this revelation about the poisoning,” says Rosenberg. “And then we consulted with the Charlotte Salomon Foundation at the Jewish Historical Museum in Amsterdam [which holds the majority of the archive] who said that it seems to be true.” The ambiguity does still leave room for others to investigate and come to a different conclusion, says Bezmozgis. “But we had to [take a view].”

There is also speculation within Salomon’s work that her grandfather was a sexual abuser. But without sufficient evidence, the film-makers decided not to include this. “We felt we’d adequately demonstrated the relationship between the two of them,” Bezmozgis says. “And that even if you take away the purported sexual abuse, there’s reason enough for her resentment to support the fact that Charlotte might do something like [poison him].”

The film assumes a level of knowledge from its audience about the second world war and the Holocaust, says Rosenberg, which accounts for the film-makers’ decision to portray little of the atrocity that Salomon would have experienced. “But I hope we managed to convey the loss and intense struggle she was going through.”

Due to its sensitive content, Charlotte is mainly aimed at an adult audience but Rosenberg says teenagers have also responded strongly to it. “Despite all the tragedy depicted, our wish is that audiences feel the sense of hope that Charlotte had through the power of her work. And the most we can ask for is that, when people leave the film, the first thing they do is Google Charlotte themselves.”

• This article was amended on 17 November 2022. The Degenerate Art exhibition of 1937 was held in Munich, not Berlin as stated in a previous version.

• Charlotte screens at the UK Jewish film festival on 15 November, and is in UK cinemas from 9 December

• In the UK and Ireland, Samaritans can be contacted on 116 123, or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at befrienders.org.