The second book in the Spark Files series, Chop and Change, by Terry Deary and Barbara Allen, successfully combines the kind of storytelling talent that keeps children hooked from beginning to end with the sneaky device of introducing real scientific experiments which ingeniously involve the reader in every twist and turn of the tale.

This time, with the sprightly Spark offspring in charge of both their kooky, deaf granny and the small, smelly Baby Spark, news of a mad axe-person rampaging through the streets on the same day the Queen is due to come for tea somehow manages to give rise to a series of experiments about changing substances. The clever intermingling of smart kids, slapstick comedy, spine- chilling adventure and scientific information makes it almost impossible to pinpoint where the fun ends and the learning starts. Children will love it all and the grown-ups will certainly approve. --Susan Harrison