Bat and Bell, the fourth title in the praiseworthy Spark Files series, is probably the most pertinent book so far and will strike a chord with anyone who is concerned about the environment. None of the humour or sheer buffoonery of the previous titles is lost when "the gran with a plan" swings into action alongside her gallant grandchildren in their battle against greedy Councillor Tripwell. As Susie and Sally Spark plan to foil his bid to dig up the graveyard and fill in the local pond flourishes, they use a series of real experiments to prove that the councillor is a baddie, allowing the reader to take an active role in the ups and downs of the story. A subject close to the heart of many a child is given the daft-Deary treatment with a bonus for would-be boffins who like to experiment for themselves. --Susan Harrison