The Heritage Of Hastur
by Marion Zimmer Bradley (1975)

Transitional novel in the popular Darkover series, with Bradley moving away from writing for younger readers and tackling decidedly more serious themes. The relationship with the Terran Empire is at the heart of a struggle on Darkover, where the telepathic inhabitants  take sides in a conflict that pits science against religion.

The Dosadi Experiment
by Frank Herbert (1977)

Often regarded as Herbert's second-best novel (behind Dune), Dosadi is a toxic planet and the setting an experiment designed to test the survival skills of any being unfortunate enough to be dumped there. A government agent of the ConSentiency - a federation of races dedicated to peace - is sent to uncover its horrors. More than worthwhile for anyone with an interest in Herbert's work.

Midnight at the Well of Souls
by Jack Chalker (1977)

Lighthearted sci-fi adventure yarn with roguish space freighter captain Nathan Brazil and his morphed companions getting into all sorts of strife on a planet known as the Well World. They set out to solve an ancient mystery, negotiating the planet's multitude of biosphere-dwelling civilisations along the way. Spawned several sequels of significantly inferior quality.

The Snow Queen
by Joan D Vinge (1980)

Despite winning a Hugo, this book is now looked upon with a fair degree of critical bewilderment. In a binary system, the long winter on the planet Tiamat is ruled over by a Snow Queen due to face ritual sacrifice with the onset of summer. She plans to hold on to power using cloning technology acquired courtesy of a stargate.

Dragon's Egg
by Robert L Forward (1980)

Amazing hard sci-fi in the grandest tradition. Dragon's Egg is a neutron star with surface gravity several billion times that of Earth. An alien civilisation develops on it almost in the blink of an eye. Forward is well-known for his groundbreaking scientific work in the field of gravitational astronomy - and it shows in this fine novel. Highly recommended.

Helliconia Spring
by Brian Aldiss (1982)

Aldiss successfully reasserted himself as one of the genre's pre-eminent authors with his popular Helliconia series. The eponymous planet is part of a system whose sun revolves around a giant star, resulting in both very short and millennia-long seasons. Spring concerns the rise of a new civilisation in one of the Great Years.

Cyteen
by C J Cherryh (1988)

A massive novel set in Cherryh's loosely-connected Union-Alliance future history. On the planet Cyteen, a powerful scientist guides the education of her clone daughter. Some may find the sheer scope and complexity of this novel a bit daunting, and opt to start instead with the wonderful Downbelow Station. Fans of Cherryh, however, won't want to miss it.

Barrayar
by Lois McMaster Bujold (1991)

The militaristic Vorkosigan family follows codes of honour and bloodthirsty rituals reminiscent of Trek's Klingons. A legendary military commander marries one of her vanquished enemies, a Vor lord. The Emperor dies and civil war looms, with her son Miles in the thick of things. Extremely popular and full of sublime humour. Close to best in the series.