My Unwilling Witch: The Rumblewick Letters by Hiawyn Oram

Jump aboard the broomstick for loads of magical fun with Rumblewick, the witch's cat, and his unwilling witch!

Dear Uncle Sherbet,
   You always said that if I was in trouble, I should turn to you for help. Now I am. HELP! It looks like my witch doesn't want to be a witch. She refuses to cackle. She won't get on a broomstick if she can help it. She's banned frogs' legs, newts' eyes, bat wings etc from our potions. AND she's completely turned against frightening children. All she wants to do is shop, watch telly and make some friends who aren't witches.

What shall I do?

Your nephew, 
 Rumblewick Spellwacker Mortimer B.