Me and my son love this story - it's just fun and funny. The illustrations are great - the pictures of bear's face when he's in a grump are funny - full of ill humour and bad will towards bearkind!
We particularly like the bit when he's in the garden and yells 'Buzz off' to a fly that's bothering him, which makes grandpa laugh (leading to the leg kicking incident). If you like this story, you should also take a look at 'The Wild Bears', which is also excellent. Enjoy!