IBM has updated their ABCs of IBM z/OS System Programming Volume 1 Redbook.
This is a good resource for anyone wanting to learn more about z/OS in general or about new z/OS features and functions.
Volume 1 provides an updated understanding of the software and IBM zSeries architecture, and explains how it is used together with the z/OS operating system. This includes the main components of z/OS needed to customize and install the z/OS operating system. This edition has been significantly updated and revised.
Here’s the link: