My Google-foo is usually pretty good, because I usually understand the conceptual framework within which I'm looking for a detail. This is not the case with the X11 system. The last reasonable overview I'm familiar with is the O'Reilly X System Administrators Guide ( http://www.amazon.com/Windows-System-Administrators-Definiti... ) from 1992 (volumes 1-7 are mostly about protocol details, primitives and libraries). Things introduced since then are a jumble to me.

What should I read for an update? I'm mostly in the Red Hat/Fedora ecosystem, which includes a multitude of upper layers.