
If you have any particular requests - it's not too late to submit. ARM64 will naturally be covered now that it's open source, as will EFI, iBoot (with detailed explanation but no source), and even SEP OS. Also aiming to provide a primer on hardware, and show detailed kernel memory management internals and IOKit in unprecedented detail (which were two notable omissions from the 1st ed due to page count restrictions).
And - there will be a hardcover, color edition. But not before early 2019.