Ivy and Bean: What's the Big Idea? by Annie Barrows (author) and Sophie Blackall (illustrator) (US edition)

Love Ramona or Clarice Bean? Check out these feisty best friends. Opposites attract! From the moment they saw each other, Bean and Ivy knew they would NEVER get on. Until, weirdly, they became best friends. Ivy is quiet and brainy. Bean is LOUD. Being so very different, they get up to lots of wacky stuff. Now it’s the Science Fair, and Ivy and Bean are all over it. The theme is global warming, and they need a Really Big Idea. Something different. Something off the wall. Something as cool as ice, in fact.