Proof that the truth really is stranger than fiction, the story of JT LeRoy is one of the greatest literary hoaxes of the modern age. An avatar created by writer Laura Albert, Jeremiah 'Terminator' LeRoy was the supposed author of several novels that shook up the literary scene in the late 1990s and early 2000s. When his fame exploded, Albert enlisted the help of her then sister-in-law, Savannah Knoop, to portray the physical embodiment of LeRoy, disguised behind a wig and sunglasses. For almost six years their caper went undiscovered.

Knoop (who today identifies as non-binary, using they / them pronouns) joins writer-director Justin Kelly as co-writer in this adaptation of their own memoir. Condensing the story, the film focuses on Knoop's experience.

Both main roles are finely cast: Knoop's especially so, with Kristen Stewart's queer, androgynous qualities working with more than subtext here. As with the metatextual backdrop to her presence in Clouds of Sils Maria, there is depth in the parallel with the intense scrutiny of Stewart's own life. Meanwhile, an almost unrecognisable Laura Dern, as Albert, convincingly makes sympathetic a woman otherwise painted as manipulative, and delightfully hams it up as LeRoy's 'manager', the cockney-accented 'Speedie'.

Yet, beyond the excellent central performances, the film never delves satisfyingly enough into ideas of identity, authenticity, or the therapeutic power of writing. It's a staid adaptation that, in its care not to sensationalise, disappointingly also steers clear of the murkier aspects of the convoluted con, ignoring questions of exploitation and, indeed, matters of consent – as in LeRoy's sexual relationship with actress-director Eva (Diane Kruger), who herself is a stand-in for Asia Argento.

In its flat presentation of a seemingly preposterous tale, Kelly's film is hardly the definitive take, though it is sure to propel viewers down a rabbit-hole of internet research, in a fevered bid to learn more.

Selected release from Fri 16 Aug.