THAT Terry Pratchett is a very funny writer is now almost universally acknowledged.

When he began setting books for younger readers on his long-established fantasy planet Discworld, there was a possibility that he might split his talents. Thankfully, such fears were unfounded; this is the third such Discworld book, and just as those aimed at adults have retained their lightness of touch, so these have sufficient chills to provide a thrill both for Pratchett's adult readers, and for children who are not too easily frightened.

A Hat Full Of Sky is a direct sequel to The Wee Free Men, though as with most Discworld books it can be read in isolation. Concerning the training in witchcraft of eleven-year old Tiffany Aching, her battle with an ancient evil and her often fraught relationships with peers and mentors, its obvious readership would be fans of Harry Potter.

The chief difference is that while JK Rowling may raise a smile at times, she seldom causes embarrassing outbreaks of giggling if read on public transport - perhaps this explains her comparatively greater success among the non-geek population.

Such dignified concerns notwithstanding, this is a gripping read which moves seamlessly between comedy, melancholy and adventure.

A Hat Full of Sky, by Terry Pratchett, (Doubleday, £12.99).