Her practice spanned a broad range of media, including installation, video, photography, painting, sculpture, performance, artist's books and writing.

A key figure in British art across four decades, she was best known for her innovative large-scale multimedia installations, and for works that took as their subject matter aspects of culture that were overlooked, marginalised, or disregarded, including paranormal beliefs–an approach which she referred to as "paraconceptualism".

"[3] Following a period where she lived in France, Wales, Morocco and India, Hiller settled in London in the late 1960s,[6] developing a practice that was innovative for its time and included a variety of media and performance-based work.

There, she presented two works, one under her own name and one using the pseudonym "Ace Posible" (a pun on "es posible", Spanish for "make it possible"): Transformer, 1973, a floor-to-ceiling grid structure with tissue paper covered with the artist's marks, and Enquires, 1973, a slide show of facts collected from a British encyclopaedia that revealed the culturally partisan definitions in what was ostensibly an objective and equitable source of information.

[3] Over the course of her career, Hiller became known for making use of everyday phenomena and cultural artefacts from our society that commonly were overlooked, denigrated, or marginalised[9] Such cultural artefacts included postcards, dreams, Punch & Judy shows, reports of UFO sightings, reports of near-death experiences, horror movies, bedroom wallpapers, street signs, ceramics, and extinct languages.

She insisted on blurring the boundaries between cultural definitions of "rational" and "irrational", at the same time reinstating the validity of the unconscious as a source of knowledge or truth.

Hiller refers to this precarious positioning of her oeuvre as 'paraconceptual,' just sideways of conceptualism and neighbouring the paranormal, a devalued site of culture where women and the feminine have been conversely privileged.

In the hybrid field of 'paraconceptualism,' neither conceptualism nor the paranormal are left intact ... as ... the prefix 'para'- symbolizes the force of contamination through a proximity so great that it threatens the soundness of all boundaries.

British artists who were taught by Hiller include Sonia Boyce, Zarina Bhimji, Tacita Dean, Douglas Gordon, and Jane and Louise Wilson.

Bringing together newly commissioned essays by a variety of artists, art historians and anthropologists–including Rasheed Areen, Guy Brett, Lynne Cooke, Jimmie Durham, Edgar Heap of Birds, and Signe Howell–it explored the fusion of myth, history and geography which leads to ideas of primitivism and looked at their construction, interpretation and consumption in Western culture.

[32] Gathering together historical and contemporary artworks, the exhibition was largely responsible for reigniting interest in the Dreamachine amongst a new generation of British artists after a period of relative neglect.