I've taken this opportunity to start off the new year with my quarterly Amazon sales rank statistics. As is often the case, the values are bouncing around quite a bit. New titles like Rose's Plone 3 for Education and Williams' Plone 3 Theming are doing well. Aspeli's Professional Plone Development is still holding its own. Plone Live (Pelletier & Shariff) is at the top of the graph, but that's an artifact of their online sales that bypass Amazon. In fact, many Plone titles are published and sold by Packt directly, which probably dilutes their sales ranks.
"Count what is countable. Measure what is measureable. What is not measureable, make measureable." -- Galileo