Here are books I recommend for small business owners about online Internet Marketing including search engine optimization (SEO), pay-per-click advertising (AdWords), affiliate marketing, conversion rate optimization and Google Analytics:
SEO, AdWords, Conv. Rate Opt. – Level: Beginner
Inbound Marketing: Get Found Using Google, Social Media, and Blogs
by Brian Halligan & Dharmesh Shah
Published Oct. 2009 by John Wiley & Sons
SEO – Level: Beginner
The Truth About Search Engine Optimization
by Rebecca Lieb
Published Feb. 2009 by Que
AdWords – Level: Beginner/Intermediate
Ultimate Guide to Pay-Per-Click Advertising
by Richard Stokes
Published March 2010 by Entrepreneur Press
AdWords – Level: Intermediate/Advanced
Advanced Google AdWords, 2nd Edition
by Brad Geddes
Published April 2012 by Sybex
Affiliate Marketing – Level: Beginner/Intermediate
The Complete Guide to Affiliate Marketing on the Web
by Bruce C. Brown
Published 2009 by Atlantic Publishing
Google Analytics – Level: Intermediate/Adv.
Advanced Web Metrics with Google Analytics, 3rd Edition
by Brian Clifton
Published March 2012 by Sybex