Vincent Zimmer at Intel) is a substantial update, incorporating the latest from the UEFI Shell specification 2.2. It includes updates on security and how-to sections on UEFI shell applications and scripts. Before the OS starts, the UEFI Shell is small, fast and light-weight manufacturing, provisioning, diagnostics and configuration environment. Go pick up a copy here.
This follows up on the revised edition of another great UEFI book, Beyond BIOS, that came out last month. Between, they serve as an unrivaled introduction into all things UEFI.