Auzou Car search and find book for toddlers

When Arthur and Rose were little, they were the heroes of the Kingdom that Roars, a world imagined in their grandfather's attic. This Kingdom was filled with things they loved: dragons, mermaids, ninja wizards, and things that scared them: especially a crow-winged scarecrow that was particularly terrifying.
Today, the twins are eleven years old, and the Kingdom that Roars is nothing but a distant memory. Arthur and Rose no longer play together. Rose is too cool for that and Arthur is too anxious about starting secondary school! But as they help their grandfather clear out the attic, Arthur, horrified, sees it disappear. Is he playing tricks on them?
Unless the Kingdom that Roars is... real?