Best SEO Books: The Truth about SEO

Wondering what the best SEO books are?

Here are the top books about search engine optimization (SEM) and search engine marketing (SEM)

The Truth about SEO (on sale for $12.91)

SEO Book by Aaron Wall ($100)

SEO on an Hour a Day ($20–on sale for $7.48)

Purple Cow by Seth Godin (???)

Also very relevant to search engine optimization:

Web Analytics on an Hour a Day by Avinash (about $20)

Don’t Make Me Think by Steve Krug (about $30 and well worth it)

Landing Page Optimization by Tim Ash (about $20–on sale for 18.89 right now)

What is your favorite SEO book or resource?