diff --git a/book_maker/cli.py b/book_maker/cli.py
index 5404b5f..0f7043a 100644
--- a/book_maker/cli.py
+++ b/book_maker/cli.py
@@ -325,8 +325,11 @@ So you are close to reaching the limit. You have to choose your own value, there
 
     options = parser.parse_args()
 
+    if not options.book_name:
+        print(f"Error: please provide the path of your book using --book_name <path>")
+        exit(1)
     if not os.path.isfile(options.book_name):
-        print(f"Error: {options.book_name} does not exist.")
+        print(f"Error: the book {options.book_name!r} does not exist.")
         exit(1)
 
     PROXY = options.proxy