Added some logic

backend/apps/books/models.py

@@ -0,0 +1,11 @@
+from django.db import models
+
+from apps.shelves.models import Shelf
+from apps.authors.models import Author
+from apps.user.models import User
+
+class Book(models.Model):
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="Authors")
+    authors = models.ManyToManyField(Author, related_name="books")
+    name = models.CharField(max_length=255)
+    isbn = models.CharField(max_length=13)