Some really top-notch information brokers contributed to this book, and it is a superb reference, well-organized, that lacks a CD-ROM with clickable links or an Online Version to which access can be gained for a fee or from a password in the printed version.
This book is extremely well-developed to the point that it can meet the needs of a first-time researcher eager to become quickly familiar with the ins and outs of the Internet, as well as the more experienced professional that wants a handy reference work to suggest new sources and methods.
The other two books are Helen Burwell's Online Competitive Intelligence, 2nd Edition: Increase Your Profits Using Cyber-Intelligence–the one book to buy if you can only buy one of these three books–and Sankey & Weber's Public Records Online, 6th Edition: The Master Guide to Private & Goverment Online Sources of Public Records (Public Records Online) (buy only if you have do work in this area or want to protect yourself by monitoring your divorced spouse's assets, etc.)
See also:
The New Craft of Intelligence: Personal, Public, & Political–Citizen's Action Handbook for Fighting Terrorism, Genocide, Disease, Toxic Bombs, & Corruption
Information Operations: All Information, All Languages, All the Time