Eva Hesse was gorgeous. As shown in the documentary that bares her name, she had that almost uncanny quality of being beautiful from any angle, while pulling any expression. Her smooth oval face seemed to be smiling at all times – the smile was in her eyes even when it wasn’t on her lips. This, it turns out, was misleading.

‘This is the story of someone who, from the outside, reveals a rather pretty picture,’ wrote Hesse in her diary. ‘Pretty face, pretty body, pretty dress. However, the person does not feel pretty inside. I have felt for the majority of my life different, alone, and apart from others.’

Hesse’s diary – lines from which are read aloud by actress Selma Blair – bears more than a slight resemblance to the journals of Sylvia Plath (and, inevitably, to The Bell Jar). Hesse’s writing has the same candid anxious self-declaring quality as Plath’s, and the authors are also uncannily alike.

They were both independent, ambitious American women who died too young. Both were a curious mixture of vulnerable and forthright; both were privileged but traumatised by their past; born in the 1930s, both had the horrors of the Third Reich doing dark things in their subconscious. And both put themselves into their work in uncomfortable, uncompromising ways.

But while it’s impossible not to be disheartened by Plath’s story, Eva Hesse’s life makes for much sunnier recounting. Although it was coloured by what one German acquaintance called traurig (sadness), it was also a life that demonstrated the benefits of art for both the artist and the audience. Significantly, Hesse didn’t kill herself; she died of a brain tumour aged 34, after three operations, still absorbed in the act of creation during periods of convalescence.

What she created was often wonderful. Her early Saul Steinberg-like illustrations later became warped sculpture, something like three-dimensional Philip Guston or Giorgio Morandi. This was Minimalism softened. Animalistic, half-wild and half-pet, her work is like a tufty stray that wanders in and out of your house at will. The strength of the documentary is that it gives weight to empty art-critic buzzwords like ‘playful’ and ‘organic’.

Hesse should be a touchtone figure for aspirant artists in the way that Plath is for young wannabe poets. The fact that she’s relatively unknown is partly due to the brevity of her artistic career, but also to the fact that she wasn’t especially careerist. The documentary innocently supposes that the 1960s were a pre-commercial time, art-wise; clearly, director Marcie Begleiter hasn’t seen the recent film Troublemakers, even though Eva Hesse socialised with Robert Smithson, one of Troublemakers’ subjects and one of the era’s most insufferable self-promoters.

Hesse also apparently shared Plath’s taste for wild womanising Celts whose male conviction and entitlement were overshadowing.

These once-radical male artists are now bespectacled and flannel-shirted, pink-faced and white-bearded. Interviewed in Eva Hesse, they look like they might be holding a cup of warm Horlicks out of sight. All that’s left of Hesse is her art, which is finally being held in high esteem.

‘The way to beat discrimination in art is by art,’ Hesse wrote. ‘Excellence has no sex.’