Intel Press published the first and second editions of these two books a few years ago, but it appears Degruyter is publishing revised third editions!
Harnessing the UEFI Shell: Moving the Platform Beyond DOS, Third Edition
Rothman, Michael / Zimmer, Vincent / Lewis, Tim
Beyond BIOS: Developing with the Unified Extensible Firmware Interface, Third Edition
Zimmer, Vincent / Marisetty, Suresh / Rothman, Michael