[Zope] Zope Book?

I'm slowly learning Zope and have read through the Zope Book 2.6 that's available from zope.org. I am also interested in purchasing an additional book to better understand using Zope. Does anyone have any recommendations? I've been using Zope for a couple months now (primarily for Plone). I'm fairly low on the learning curve and would like to find a good overall book on the subject. Does anyone have any recommendations? Thanks in advance, Shane Graber