If you're committed to actively supporting your book, it's best to stake out your own territory on the Web. This means registering your own domain name, which you alone control. GoDaddy.com, Register.com and NetworkSolutions.com are well known, reliable firms where you can buy a package of services--domain registration, Web hosting and e-mail accounts.
You may want to use the title of your book as the domain. Authors with more than one book often register a new domain for each book, or simply use a different folder on their site for each book, such as #www.JaneDoe.com/Book1# and #www.JaneDoe.com/Book2#.
Keep your domain name short and memorable so people who see it or hear of it can recall it. Hyphenated domain names are usually a bad idea--they're harder to remember and they fail the "radio test" because they're difficult to repeat in conversation.