I just spotted Google Trends on the Google Labs page. Type in a keyword, or more than one, separated by commas, and Google gives you a line graph of search volume for about a two-year period. Below that you get a bar graph of search volume by city, region or language.
Here is what I found out: Searches for ‘seo’ are significantly greater than searches for ‘search engine optimization’. In fact ‘seo’ searches are increasing with ‘search engine optimization’ in decline.
What’s more searches for ‘sem’ are substantially greater than both ‘seo’, ‘search engine optimization, and ‘search engine marketing’, and showing continued growth.
Trends does seem to have some significant holes when it comes to keywords. Searches that I would think are common return with nothing:
Your terms – seo book – do not have enough search volume to show graphs.
I was going to show a quick comparison to WordTracker stats, but WT is broken at the moment!