Do you mean books by:
* C.S. Lewis: If so, his books are published by various publishers, including HarperCollins, Houghton Mifflin Harcourt, and Penguin Random House.
* C.S. Forester: If so, his books are published by various publishers, including Random House, Penguin Random House, and the Folio Society.
* "CS" books as a general category? If so, please provide more context.
Once you clarify what you mean, I can help you find the publisher.