Fans of late British author Terry Pratchett, many in science-fantasy costumes, queued outside bookshops overnight as the final instalment in the Discworld series went on sale Thursday.

"The Shepherd's Crown", the 41st in the saga, went on sale at 2300 GMT in Britain and Commonwealth countries, and immediately received five-star reviews in Thursday's newspapers.

Waterstones in central London was one of the shops to open on the stroke of midnight, and the author's friend Rob Wilkins read an extract of the book to 200 ticket-holders.

Pratchett died in March aged 66 after a long battle with Alzheimer's disease and his Discworld novels are some of the best-selling works in English fiction around the world.

The series is set on a flat world balanced on the back of four elephants which themselves stand on the shell of a giant turtle.

He wrote the first book in the series, "The Colour of Magic", in the late 1960s although it was not published until 1983.

"The Shepherd's Crown" book was completed last summer, before he succumbed to the final stages of his disease.

"This isn't just a great Discworld book, it's extraordinary; a proper send-off for Pratchett and this mammoth series," wrote the Daily Telegraph's Kat Brown.

"In this, his 41st Discworld novel, now his last, Pratchett gets his house in order beautifully," she added.

"With his final Discworld tale, the late author continues his move away from pure fantasy and into moral and social exploration," wrote Guardian reviewer A.S. Byatt.

"We shall miss him," she added of Pratchett.

"His loss is a persisting embuggerance," she said, using a word he coined to describe his Alzheimer's.

Pratchett, who sold more than 85 million books worldwide, was a fan of science fiction from his youth and wrote his first Discworld novel to make fun of the rival fantasy genre -- but the target of his satire later came to define his work.

The novel will go on sale in the United States on September 1.
Source: AFP