     let isbn: String
     let authorIntroduction: String
     let summary: String
+    var series: Series?
 }
 
 // MARK: CodingKey

        let title: String
    }
    
}


        case isbn = "isbn13"
        case authorIntroduction = "author_intro"
        case summary
        case series
    }
}
// MARK: Inner Struct Defines
