def book_list(request, format=None):
    """
    List all users, or create a new user
    """
    if request.method == 'GET':
        users = Books.objects.all()
        serializer = UsersSerializer(users, many=True)
        return Response(serializer.data)
    elif request.method == 'POST':
        serializer = UsersSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
def book_detail(request, pk, format=None):
    """
    Retrieve, update or delete a user instance
    """
    try:
        user = Books.objects.get(pk=pk)
    except Books.DoesNotExist:
        return Response(status=status.HTTP_400_NOT_FOUND)

    if request.method == 'GET':
        serializer = UsersSerializer(user)
        return Response(serializer.data)
    elif request.method == 'PUT':
        serializer = UsersSerializer(user, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
    elif request.method == 'DELETE':
        user.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)