This is is a Japanese-language book or magazine devoted to fashion or cosplay ("COStume PLAY"), and may contain actual sewing patterns for creating your own clothing/costumes, as well as photos of completed outfits.
For the hard-core goth and goth-loli dressers out there, this thick magazine is devoted to advertisements for shops carrying materials, finished clothing, and accessories -- even "gothic lolita tableware", if you can believe it!