He is the author of the novel The Night of the Triffids, the novella Humpty's Bones, and the short story Goblin City Lights, which have all won awards.

Clark's first book for the American market, Darkness Demands, was set in the small English village of Skelbrooke, South Yorkshire.

[7] In August 2023, Clark signed a three-book deal with Darkness Visible Publishing, run by author Roger Keen, which inaugurated the Blood Crazy Series.

It concerns nineteen-year-old Nick Aten, caught up in a maelstrom when the entire adult population becomes murderously unhinged and is driven to annihilate every young person below the age of twenty.

The second book, Blood Crazy: Aten in Absentia, features a new community and their struggles with a mystery illness, together with the emergence of curious personality changes to the ‘Creosotes’ (the murderous adults), which pose unknown threats.

The third book, Blood Crazy: Aten Present, sees the return of Nick and other favourite characters, who are caught up in a new apocalypse as the transformed adults wreak havoc on a greater scale.

[8] In 2002 Clark won the British Fantasy Award for best short story, "Goblin City Lights", and best novel for The Night of the Triffids.

[17] However, His Vampyrrhic Bride was described as "romantic without being soppy or sentimental", and "a palate cleanser for horror readers tired of the same old blood-suckers".

[19] The reviewer for Death's Dominion wrote that "all the monster-burning, skull-crushing, village-razing, castle-raiding fun ... make for a satisfying son of Frankenstein".