Singer Carey, whose "All I Want for Christmas Is You" is in near-constant rotation each holiday season, makes the leap to Christmas picture book with co-author Davis. Little Mariah lives in a worn, shabby house in a wealthy neighborhood; though poor, she has a kind nature and musical talent--both of which ultimately save her. Taunted by a nasty brother-sister duo who enter her home uninvited, Little Mariah is distracted by snowfall and runs out into the nearby woods. The snow transforms into Snowflake Butterfly Fairies. Following these entrancing visions, she encounters a gang of bullies but, having tripped over a heart-shaped stone, she uses its magical properties for good in a convoluted series of events. The Butterfly Fairy Queen arrives and crowns Little Mariah the Christmas Princess for her "perfectly pure songs from the heart." Back at Little Mariah's house, which has been miraculously transformed, Little Mariah performs Carey's uber-hit Christmas song. Overwritten, overwrought, overlong, and narrated in clunky verse, this holiday story, seemingly inspired by Carey's early childhood and with "Little Match Girl" and "Cinderella" vibes, rambles while making its trite, albeit well-meaning, point. It will attract attention because of the star power of its co-author; note her empowering foreword. The colorful illustrations are cheery. Wide-eyed, blond-curled Mariah and the Fairy Queen have light-tan skin; Mariah's mom and several other characters, including the bullying brother and sister, are pale-skinned; the fairies are diverse in skin tone. (This book was reviewed digitally.) All we want for Christmas is a more coherent story. (Picture book. 4-7) Copyright (c) Kirkus Reviews, used with permission.