"int - Matches zero or any positive integer". Dirty fix.

books/urls.py

@@ -4,5 +4,5 @@ from . import views
 urlpatterns=[
 	path('',views.index,name='bidex'),
 	path('<str:bookurl>',views.book,name='bbook'),
-	path('<str:bookurl>/<int:chapnum>',views.chapter,name='bchap'),
+	path('<str:bookurl>/<str:chapnum>',views.chapter,name='bchap'),
 ]

books/views.py

@@ -58,5 +58,5 @@ def book(bookurl):
 @rerender
 def chapter(bookurl,chapnum):
 	book=models.Book.objects.filter(url=bookurl)[0]
-	chapter=models.Chapter.objects.filter(book=book,number=chapnum)[0]
+	chapter=models.Chapter.objects.filter(book=book,number=int(chapnum))[0]
 	return {'title':chapter,'content':'<p>Navigation buttons will come later...</p>\n'+chapter.contents,'date':chapter.added}