I have a question. Do you know if, as a newly published author with a lovely new website, do I have to get a Sales and Use Tax number [from my state] to be able to sell books right off of my site? I'm not sure who to ask about sales tax on the web. Thank you so much for all of your invaluable knowledge.
Yep. If your state has a sales tax and expects you to collect it on items sold over the Internet, then yes, you're going to need a tax number to do business.
Most states will have a website that explains the rules and how to do it. For Utah, you go here.
For other states, google your state name and state sales tax. Example: "California State Sales Tax".
If you don't want to deal with this, it may be easier to put links to Amazon, Barnes and Noble, and/or your publisher.