I have a mental image of Ally Kennen sitting down with a checklist before she started writing Midnight Pirates, upon which were inscribed all the best possible ingredients for a Rollicking Adventure Story. Feisty siblings? Check. Absentee parents? Check. Mysteries, mayhem and mermaids? Check. Pirates? Ghosts? A dodo? Three more big green ticks. Everything is here that should and indeed could be here, but I don't for one minute want to suggest that it feels as though it was written by numbers. Indeed, one of the principal delights of this happy book is that you can never be sure where it's heading next. Is it a family drama or a boarding school romp? Will pirates or ghosts be the main bill of fare? Kennen keeps us guessing for a good long while.

The MacNamara family, comprising Irish father, Mauritian mother and three wayward kids, are the hapless owners of the Fawlty Towers-like Dodo Hotel, which sits rather improbably on a forgotten stretch of Cornish coast. Revealing that the hotel has been struggling for far too long, the parents announce that not only are they putting it up for sale, but that their offspring are to be dispatched to a local boarding school while they go to a wedding in Mauritius. For nine weeks.

It is at this point that the book comes alive, as the youngest of the three, 10-year-old Jackie, refuses to be separated from his faithful mongrel, Fester. Before anyone can blink, he, his elder sister Miranda and their elder brother Cal have all run away  not from home, but back to the now deserted hotel, to see how long they can get away with hiding out in their own house before they're discovered.

Jackie, much to his siblings' horror, manages to snare some new guests for the hotel, unaware that the place is actually closed. The real identity of these guests sends the book charging out in a whole new direction, and real dangers sail over the horizon and straight towards the Dodo.

Kennen manages to steer a safe course between the treacherous rocks of fictional impossibilities and unbelievable plot turns: she doesn't duck the question of "what would really happen", but sails confidently into even more enjoyably ludicrous territory. The success of this is down to her strong characterisation; Miranda, our long-suffering protagonist, is the sanest of everyone, but her brothers provide welcome lunacy, with Cal appearing to believe he should have been born in California in the 1980s, and Jackie a vortex of strangeness in the way only small boys can be. Supporting characters have not been skimped on, with many wonderful weirdos adding to the peculiar sense of place.

Kennen's book reminded me of another great adventure for a similar age group, also set on the Cornish coast: Dead Man's Cove by Lauren St John. As anyone who knows Cornwall will understand, both St John's book and Midnight Pirates are set in a world that resembles our own modern one, and yet in which unusual things are always just around the corner, waiting to surprise.

And isn't that what we hope for from a book when we're young; the proof that magic is really all around us?

 Marcus Sedgwick's Revolver is published by Orion.