Plone 3.3 Site Administration: Manage Your Site Like a Plone Professional by Alex Clark is a book firmly targeted towards Plone administrators. Web site administrators are seldom treated to a whole book devoted just to them, but here's one written just for that audience. Front to back, this book is full of material meant for admins only.
The book is mostly concerned with instructing the reader on using Buildout, the preferred tool for installing add-ons to Plone-powered web sites. There is a great deal of text devoted to coaching the reader exactly through the installation of many useful add-ons. Some of these include cache agents, front-end proxies, themes to improve your site's appearance, and more. There is one strong caveat — this book is all about how, not why. If you don't know what a cache agent does, or why you'd want one, this book is not going to help you much. But if you know you need one (and even more so if you have an inkling which one you want), this book will help a great deal.
Additional tips are given on security, site setup, future directions for Plone, and more. If you're in the target audience (Plone administrators), you're going to want to have a look at this book. If you're a Plone developer, or just learning Plone — then you might want to start with some more remedial material first.
The book can be found here: https://www.packtpub.com/plone-3-3-site-administration/book