Araminta Spook: The Sword in the Grotto by Angie Sage

What do you buy someone for their 500th birthday? Araminta is desperately trying to think of the perfect gift for her favourite ghost, Sir Horace, but it’s hard to buy gifts for someone with no specific hobbies, and no body. Then an inspired idea leads to trouble when all does not go as planned, and Araminta wonders whether she’ll ever see Horace or her family again, let alone have time to organise the party.