Sir Terry Pratchett's final Discworld novel has hit the shelves as fans gathered for a midnight release.

Readers eager to get their hands on copies of The Shepherd's Crown, the 41st and last in his popular Discworld series, queued outside bookshops, many in fancy dress.

And the book met with rave reviews from critics, who hailed it as a "magnificent sign-off".

Sir Terry, who died in March aged 66 after battling Alzheimer's disease, sold millions of copies of his books set in his comic creation of Discworld - a flat disc balanced on the backs of four elephants standing on the back of a giant turtle.

The Shepherd's Crown, which he wrote last year, is the fifth book featuring the young witch Tiffany Aching.

Kat Brown in the Telegraph gave the novel five stars, saying "Pratchett gets his house in order beautifully".

She wrote: "This isn't just a great Discworld book, it's extraordinary; a proper send-off for Pratchett and this mammoth series.

"It is entirely Pratchettian to give the reader an opportunity to mourn fiction and reality at the same time ... This last is a magnificent sign-off."

The Independent's David Barnett, pointed out Sir Terry was aware the book would be his last.

He said: "As such, it's difficult to see The Shepherd's Crown as anything other than Sir Terry's farewell letter to his legion of fans - though of course, this being a Pratchett, it's a pretty fine novel in its own right.

"The Shepherd's Crown is a sometimes sad, often funny and eminently suitable testament to the life and career of Terry Pratchett."

AS Byatt, writing in the Guardian, praised the novel as he described the author's loss as a "persisting embuggerance".

"He wrote increasingly about worlds in which real harm happens and increasingly about real efforts to prevent it. In The Shepherd's Crown, which is part of a group of novels claiming to be for 'young adults', evil and anger still take the form of fairy story and myth. But the reader experiences them sharply.

"Nothing in Pratchett stays still and his inventive energy, book after book after book, is astounding."

Waterstones, in Piccadilly, London, created a Discworld inside its store and greeted fans in fancy dress, including as the wizard Rincewind, while others queued at the chain's Newcastle store dressed as witches, wizards and even Death, a regular character in Sir Terry's hit series.