How to learn about all the parts of the linux operating system?

Hi, I'm a linux sysadmin, and I have been for a long time now. But I realize that there are still parts of Centos I don't know or understand.

Most books talk about how to use linux, text manipulation, commands, etc.

I'm looking for a book, or resource that really talks about the kernel, and the integral parts that make up a RHEL/CENTOS install. I really want to get the big picture.

Thanks.