What can you tell me about his later works?
It's surrealist, subversive, antiauthoritarian, existentialist, irrationalist and arguably neo-Luddite. If his early work was shaped by his experience of the First World War, his late work was shaped by his experience the Second—particularly of the Nazi regime. It retains some elements of his earlier work though, such as his heroicism, which takes the form of vanguardism (albeit of a non-Marxian sort).
I remember reading On the Marble Cliffs a long time ago, which really shows his disillusionment with NS Germany. I didn't realize he was so prolific after the war too.
Pic related is another very relevant author that's sadly not read today as much.
>What can you tell me about his later works?
Considerations on France, most definitely. Then the Generative Principle of Political Constitutions, then On the State of Nature. Those are his three major works I would say. Once you're done with them and feel like going a step further I would recommend The Saint Petersburg Dialogues, but this is more about theology than politics per se; it's a great reading regardless.
Regardless of what you read I would also suggest you find a good secondary source to follow up on, since some contextualization and systematization might be in order (there are plenty of good secondary works, just stay away from Isaiah Berlin).
Remember also that Joseph de Maistre might seem pretty odd and out there, especially at first reading, but he thought very, very hard on every line that he put down and nothing is gratuitous or exaggerated.