Giants of speculative fiction including Stephen King, Neil Gaiman and Margaret Atwood have made way for newcomers on a lively shortlist for this year's Arthur C Clarke award for the best science fiction novel of the year.

The UK's most prestigious science fiction prize will see American author Ann Leckie's first novel Ancillary Justice – a space opera about a spaceship trapped in a human body – competing with Egypt-born Ramez Naam's debut Nexus, in which an experimental drug links human beings mind to mind. A third debut also makes the line-up: American novelist Kameron Hurley's God's War, about a bisexual bounty hunter who collects the heads of deserters.

James Smythe, a growing force in British science fiction, makes the cut for The Machine, set in a near-future dystopia where memories can be recorded on machines. The list is completed with novels from two well known names in science fiction: former winner Christopher Priest, chosen for The Adjacent, and Phillip Mann, picked for his first novel since 1996, The Disestablishment of Paradise.

The books were selected from 121 submissions, which were made public by the award following controversy around last year's all-male shortlist. This year, said director Tom Hunter, 34 books were submitted by female writers, a ratio of "approximately one in four, [of which] one in three made it through to the discussion list of 30 titles from which the judges made their final selection today". This ratio "carried through into the final six shortlisted titles, two of which are by new female authors," said Hunter.

He called the shortlist "such an excitingly fresh list, which really reflects new writers as well as classics of the genre". The line-up, he said, shows the "real vibrant health" of science fiction today, with submissions received from 42 different publishing houses and imprints. "There's a lot of energy in the genre at the moment," said Hunter.

Titles which failed to make the final cut for this year's Arthur C Clarke award include books by giants of the genre Terry Pratchett, Alastair Reynolds and Kim Stanley Robinson, as well as Ruth Ozeki's Booker-shortlisted A Tale for the Time Being, Atwood's MaddAddam and King's Doctor Sleep.

The judging panel features Ian Whates and Duncan Lawie from the British Science Fiction Association, and Sarah Brown and Lesley Hall from the Science Fiction Foundation, along with Georgie Knight from the Sci-Fi-London film festival. The winner of the award, who receives a cheque for £2014, will be announced on 1 May and will join an illustrious roster of former winners including Atwood, M John Harrison and China Miéville.

The shortlist in full

God's War by Kameron Hurley (Del Rey)

Ancillary Justice by Ann Leckie (Orbit)

The Disestablishment of Paradise by Phillip Mann (Gollancz)

Nexus by Ramez Naam (Angry Robot)

The Adjacent by Christopher Priest (Gollancz)

The Machine by James Smythe (Blue Door)