책이랍니다 = 책이라고 합니다.^^ "-랍니다" is short for "-라고 합니다", and it can mean "sb says/said that..." or "it is called ..." (*sb = somebody) This kind of the style of the speech is called "하십시오 체" or "합쇼체", here "체" means "style". As to the speech styles, Nice to meet you. 1) "하십시오" 체 = 만나서 반갑습니다(polite and formal) 2) "해요" 체 = 만나서 반가워요(polite and informal, commonly used in daily conversation) 3) "해" 체 = 만나서 반가워(not polite and informal, used among close friends) \^o^/