The Web is for book selling. You’ve got to be strategic in how you market yourself and your work. Book selling is way beyond the bookstore—in fact, book stores are minor players for many authors. It makes sense to be on Facebook (growing in leaps and bounds), LinkedIn (business connecting) and MySpace (the under 25 crowd); to send out tweets on Twitter (if you have different hats of expertise, more than one Twitter account makes sense); create videos for YouTube and actively use your website (you do have a website that is updated regularly, yes?).
If you have a new book, make sure you get it posted, with cover on your main pages within these groups. You can get the word out about your books via participating on content sharing sites that would in turn, be able to link back to you. Check out HubPages.com and Squidoo.com—post tips and tidbits—viewers will get use to seeing your name, reading your words and then find your work.