{% for review in book.reviews.all %}
<li>{{ review.review }} - {{ review.author }}</li>
{% endfor %}

class Book(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    title = models.CharField(max_length=255)
    author = models.CharField(max_length=200)
    price = models.DecimalField(max_digits=6, decimal_places=2)

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('book_detail', args=[str(self.id)])

class Review(models.Model):
    book = models.ForeignKey(Book, on_delete=models.CASCADE, related_name='reviews')
    review = models.CharField(max_length=255)
    author = models.ForeignKey(get_user_model(), on_delete=models.CASCADE)

    def __str__(self):
        return self.review

book.reviews.all

book

reviewS

review

book = Book.objects.get()
related_reviews = book.reviews.all()   <-- тут будет итерируемый объект из объектов типа Review, у которых есть ForeignKey  к этому конкретному Book

class Review(models.Model):
    book = models.ForeignKey(Book, on_delete=models.CASCADE, related_name='reviews')