So here are my unbiased thought on the same:
Nokogiri - is an HTML, XML, SAX, & Reader parser with the ability to search documents via XPath or CSS3 selectors… and much more
This book is in its simplest and easiest form, explains the basics of Nokogiri in a layman's language.
A definite read for all those who love simplicity and awesomeness of ruby language.
Book is in interest of those new-comers who would like to learn scraping data from 'websites/other sources' which does not provide a developer API.
It does not have any fancy graphics, no vague examples etc. It just dives into the real subject , which is what a beginner (or expert for that matter) would require to get started or master Nokogiri.
With very subtle examples of data scraping and clear understanding, the author makes a newbee feel like they already know how Nokogiri works.
The section "Top 13 features you need to know about" clearly explains some of the not known features of Nokogiri. My favorite parts are about "Spoofing browser agents" and "Mechanize".
All in all this is perfect book for beginners. But if you are an expert ruby developer and use nokogiri extensively, this book may not be for you.
For a first time user, I definitely recommend this book.
You can get a copy from these places:
Some Nokogiri Info:
sudo gem install nokogiri