admin.py

from django.contrib import admin
from .models import Author, Book

class BookInline(admin.TabularInline):
    model = Book
    readonly_fields = ['slug']

class AuthorAdmin(admin.ModelAdmin):
    inlines = [BookInline]

admin.site.register(Author, AuthorAdmin)

models.py

from django.db import models
from django.template.defaultfilters import slugify

class Author(models.Model):
    name = models.CharField(max_length=200)

    def __unicode__(self):
        return self.name

class Book(models.Model):
    author = models.ForeignKey(Author)
    slug = models.SlugField(primary_key=True)
    title = models.CharField(max_length=200)

    def __unicode__(self):
        return self.title

    def save(self, **kwargs):
        if not self.slug:
            self.slug = slugify(self.title)
        super(Book, self).save(**kwargs)