The Inspiration Works Disney Princess Magical Secret Book is just the sort of thing I would have loved when I was little, and right now it's down in price from £21.99 to £11.99 at Amazon.
Suitable for little princesses aged three years and above, this magical secret book can be opened with the secret key, and it comes with a special pen as well as a ring and bracelet, presumably fit for a princess.
Inside you'll find a book of fun activities to keep your little princess entertained, but to be honest I don't think I'd have cared what was inside this when I was a kid - I would have just loved the magical secret fun of it all.
The reviews are a wee bit mixed - out of 26 reviews, only 8 customers have rated this item worth 5 stars or more, but that seems to be partly in relation to the normal price so I reckon at £11.99 you're getting decent value for money, but it'd be a disappointment at the normal price.
As ever, delivery will be free since you're spending more than £10 in one transaction.