URL設計やり直し
これで、いこう。。
GET /book_register # 新規入力画面
POST /book_register # REDIRECT TO /book_register/confirm GET /book_register/comfirm POST /book_register/confirm # REDIRECT TO /book_register/complete GET /book_register/complete GET /book/:id/input POST /book/:id/input # REDIRECT to book/:id/comfirm GET /book/:id/comfirm POST /book/:id/comfirm #REDIRECT to /book:/id/complete GET /book/:id/complete