Huw Aaron’s tale of a green blob reading to its child takes overall prize, while Janeen Hayat wins in the young readers category and SF Williamson in the older readers

This year’s Waterstones children’s book prize winner features a green blob tucking its child – a smaller green blob – into bed.

Sleep Tight, Disgusting Blob by Huw Aaron is narrated by the parent blob who, through the course of the book, tells the child blob about all the other creatures also getting ready to sleep, including a yeti, Medusa and a Minotaur.

Aaron, a Welsh author and illustrator, was announced as the winner of the £5,000 prize at a ceremony on Thursday evening. His book topped the illustrated books category before going on to be named overall winner.

Booksellers, who vote for the prize, praised Huw’s “dreamy, painterly style and sweet rhyming text”, said Bea Carvalho, head of books at Waterstones.