now updating existing fields on Books works correctly

Deokhyun_Lee_reading/bookshelf/templates/books/book_details.html

@@ -23,7 +23,7 @@
         <p>No Available Books.</p>
     {% endif %}
     <ul>
-    <li ><button type="button" onclick="alert('You pressed the button!')">Click me!</button></li>
+    <li ><button type="button" onclick="window.location.href='/books/{{book.pk}}/edit'">Edit Books</button></li>
     <li><a href="/home">Home</a>&nbsp&nbsp&nbsp&nbsp&nbsp<a href="/books">Books</a>&nbsp&nbsp&nbsp&nbsp&nbsp<a href="/authors">Authors</a></li>
 </ul>
 {% endblock %}
\ No newline at end of file

Deokhyun_Lee_reading/bookshelf/templates/books/edit-book.html

+{% extends 'base.html'%}
+{% block title %}
+Add New Book
+{% endblock %}
+{% block content %}
+    <form method="post">
+        {% csrf_token %}
+        {{ form.as_p }}
+        <button type="submit">Save Changes</button>
+  </form>
+{% endblock %}
\ No newline at end of file

Deokhyun_Lee_reading/bookshelf/urls.py

 from django.urls import path
-from .views import HomeView, AuthorListView, AuthorDetailView, AuthorAddListView ,BookListView, BookDetailView, BookAddListView
+from .views import HomeView, AuthorListView, AuthorDetailView, AuthorAddListView ,BookListView, BookDetailView, BookAddListView, BookEditView
 
 urlpatterns = [
     # for Home (landing page)
@@ -7,9 +7,11 @@ urlpatterns = [
     # for Authors page
     path('authors/', AuthorListView.as_view(), name='authors'),
     path('authors/<int:pk>/details', AuthorDetailView.as_view(), name='author_detail'),
-    path('authors/add',AuthorAddListView.as_view(), name="add_author" ),
+    path('authors/add', AuthorAddListView.as_view(), name="add_author" ),
+    
     # for Books page
     path('books/', BookListView.as_view(), name='books'),
     path('books/<int:pk>/details', BookDetailView.as_view(), name='book_detail'),
-    path('books/add',BookAddListView.as_view(), name="add_book" )
+    path('books/add', BookAddListView.as_view(), name="add_book" ),
+    path('books/<int:pk>/edit', BookEditView.as_view(), name='book_edit')
 ]
\ No newline at end of file

Deokhyun_Lee_reading/bookshelf/views.py

 from django.views import View
 from django.shortcuts import render, redirect
-from django.views.generic import ListView, DetailView, CreateView
+from django.views.generic import ListView, DetailView, CreateView, UpdateView
 from django.shortcuts import render
 from .models import Author, Book
 from .forms import AddBookForm, AddAuthorForm
@@ -56,6 +56,23 @@ class BookAddListView(CreateView):
             return redirect('book_detail', pk = new_book.pk)
         else:
             return render(request, 'book_details.html', {'form': form})
+        
+class BookEditView(UpdateView):
+    model = Book
+    form_class = AddBookForm
+    template_name = 'books/edit-book.html'
+
+    def post(self, request, pk):
+        form = AddBookForm(request.POST)
+        if form.is_valid():
+            # onSave is called, the form will have essential data and this includes pk as well. 
+            new_book = form.save()
+            # pass the pk and redirect. 
+            return redirect('book_detail', pk = new_book.pk)
+        else:
+            return render(request, 'book_details.html', {'form': form})
+
+
 
 class AuthorAddListView(CreateView):
     model = Author