Brutalist buildings — you either love them or hate them, though the number of people that fall in the former category is increasing, according to an architecture writer.

The concrete structures that often resemble stacked cement toy boxes built with raw textures are divisive and date back to the post-war period.

"You often think of it being a relic of the communist era," UK author Christopher Beanland said.

"They were often buildings designed for the people, so you have social housing like the Sirius building or universities."

The future of the Sirius building in The Rocks has been in doubt following the eviction of most of its public housing residents.

While it was once considered an eyesore by the National Trust, it is now at the centre of a protection battle by the Heritage Council which hopes to save the building from being sold by the State Government.

"I think people are rediscovering the weird beauty of these buildings," Mr Beanland said.

"They are strange places, they're not to everyone's taste.

"The weirdness of it is one of the things that appeals to me, but it's also different to a lot of architecture we see now that is often flimsy and quite shoddy a lot of the time. And these were sort of solid, meaty constructions."

According to Mr Beanland, who recently released a book titled Concrete Concept, Brutalist Buildings Around The World, opinions about brutalist architecture are changing.

"People are discovering these buildings due to art and photography and books and films that people are making," he said.

"A new generation is discovering them."

Mr Beanland told ABC 702 Sydney that he fell in love with the variety of brutalist buildings in Sydney on his recent trip to Australia.

Sirius building

Residents of the Sirius Apartment in The Rocks were moved out ahead of the sale. ( ABC News: Jayne Margetts )

The Sirius building sits in the prime location overlooking Sydney Harbour and the Opera House.

It was built in 1979 for public housing tenants displaced during the 1970s when the area was being redeveloped

Most residents were moved out throughout 2015, despite protests.

UTS Tower

Derided by some, but admired by fans of "brutalism", the UTS tower in Sydney. ( Photo: Andrew Worssam )

It is the building that many love to hate.

University of Technology Sydney's UTS Tower was designed in 1964 and is featured in the State Library's latest exhibition marking the 200th anniversary of the Government Architects Office.

Curator Dr Charles Pickett told the Sydney Morning Herald that while the UTS building was a "miss" in terms of its aesthetic presentation, it was incredibly functional.

"I am actually quite fond of it," he said.

School of Molecular Bioscience and Biochemistry, University of Sydney

Christopher Beanland says buildings at the University of Sydney are some of the best examples of brutalist architecture. ( Supplied: Christopher Beanland/Frances Lincoln )

Mr Beanland calls this building at the University of Sydney "the pick of the bunch" in his latest book.

He writes: "Set in green parkland in Darlington, the school combines a grumpy frontage with a dizzying array of steps, walkways and levels, and concrete seemingly mixed with Shredded Wheat.

"It seems oddly suited to the scientific experiments that take place within."

Reader's Digest building

The Reader's Digest building on Waterloo Street in Surry Hills is set to undergo an energy-efficient overhaul. ( The Twentieth Century Heritage Society of NSW )

This commercial office building in Surry Hills is described by Mr Beanland as "a chummy combination of offices, printing house and warehouse clinging to a slope in a leafy backstreet".

Last year, the Reader's Digest building was signed up to receive a $1.2 million energy efficiency infrastructure upgrade.