With her latest book, Sparks, longlisted for the Guardian children's fiction prize, Ally Kennen has abandoned a key element of her award-winning formula. Unlike previous titles Beast, Berserk and Bedlam, this offering doesn't begin with the letter B. It does, however, still contain all the ingredients of a mighty fun read. Sparks also has a subtitle, one which neatly sums up the premise of the entire book: "How to give Grandpa a Viking funeral".

Grandpa loved boats. In a letter to Carla, one of his grandchildren, read after his death, he reveals that he would have loved to have had a Viking-style funeral, with his remains "sent out to sea on a burning boat at sunset, to sail off into eternity". But he knows this is illegal, so he asks Carla to burn some important letters in that manner instead. (These letters were obviously ancient love letters between Grandpa and a woman who wasn't Grandma.)

But Carla can't get the image of the burning longboat out of her mind. It soon becomes apparent to the reader that Grandma was not universally loved by the family when living; and Carla really doesn't like the idea of Grandpa having to lie next to Grandma in the churchyard for eternity. What, then, if she really was to carry out his wish? What if she could somehow get Grandpa's body out of the undertaker's, on to his boat and out to sea, in a blaze of flame?

But who can Carla trust to help her, aside from her sister Penny and brother Woody? She settles for the Sparks, members of the Little Wichley Carnival Club. These children have a float in the upcoming Bigwich Carnival, which falls on the same day as Grandpa's funeral. She persuades them to change the theme of their float from Bananas in Pyjamas to Go Valhalla! Now they have a way of getting their Viking burial boat through town.

Today in the UK, over 70% of dead people are cremated. Back in February, a Hindu man won the right in a British court to be burned on a traditional outdoor funeral pyre after his death. But a Viking funeral? As an adult reader, you just know that there's no way Grandpa's body is really going to end up being burned at sea, especially not in a family-based children's novel of this nature. This isn't a zany anything-could-happen romp, but is rooted in reality. Part of the fun is wondering just how close to succeeding the children will get and how they will eventually be thwarted. Getting a coffin out of the local morgue isn't child's play. A child reader, however, may well assume that anything could happen. The nearer I got to the end, the more I found myself thinking that there weren't enough pages for the burning not to take place. Surely it couldn't . . . No! But . . .

There are some wonderfully comic and exciting moments in Sparks, including one where a dummy run goes disastrously wrong, leading to a serious security incident involving the local nuclear power station. Sparks is funny, entertaining and surprisingly moving and it is this  the relationship between members of the family, including that between Carla and the memory of her dead grandfather  that lifts the book above the ordinary. The fact that Mum has lost her father is not neglected. The fear of how she will react if Carla and the others are successful is one of the many dilemmas explored. In the end, though, what is left is love.

Philip Ardagh's latest Grubtown Tale, Trick Eggs and Rubber Chickens, is published by Faber.