We think crime writer Val McDermid's first children's book is a real winner. Isobel loved the bright cover, featuring a smiling, bespectacled granny swinging from a rope and wielding a cutlass. The story of a granny, who "captured many pirate ships but was always home for tea," successfully mixes the familiar with the fantastical.

Isobel liked how the story began, with the grandson letting the reader into the secret that his granny was a pirate. I thought this was a friendly, inviting way to start the book, not unlike Grandpa In My Pocket on CBeebies, also featuring a silver haired relative with special powers. Instead of a shrinking cap, Granny wields her handbag to devastating effect, inspired by an idea from McDermid's own son.

The rhymes are simple and fun, making the book a pleasure to read aloud and the illustrations are colourful and full of humorous details. Isobel liked the pirates "long wriggly noses", Granny's pirate dog Jolly Roger with his "sharp teeth" and Granny sitting in her rocking chair near the end in her slippers with a half-eaten roll.

We did think the story might appeal more to boys and Isobel said the pirate part of it didn't really interest her. At the same time, putting a granny in a traditionally masculine role works well. This, together with the quality of the rhymes and vividness of the illustrations, mean My Granny Is A Pirate will stay in the imagination of young readers long after they've closed the book.

If you would like to become a family reviewer, email us at childrens.books@theguardian.com