I just finished a book tour as a first-time author. Here's what I can tell you.
First, product matters most. Getting great stories out quickly is the most important thing.
Second, on the other hand, if nobody knows about your stories, you're never going to get word-of-mouth, which is the biggest factor for people new to an author http://johndbrown.com/2009/05/how-readers-select-books/ and is an important factor to library sales, although not the top factor http://johndbrown.com/2009/09/how-libraries-select-books/.
So you have to get your book noticed. Publishers have a lot to do with this. They get you in front of booksellers, get you interviews, do all sorts of stuff. When they pay you $750,000 for three books (Stephenie Meyer), you can bet they're going to go all out with various PR & Marketing programs because they're hoping to make a lot more than $750,000 back. That's just the author's royalty which is a small part of total revenues.
What about when you get the average for a new SFF author http://www.tobiasbuckell.com/2005/02/07/how-much-does-a-science-fiction-or-fantasy-writer-make/? Well, they're not going to placing radio ads, I can tell you that.
But large or small, how does a book tour affect sales? Well, look at what it takes to become a best-seller: http://johndbrown.com/2009/04/how-many-copies-makes-a-best-seller/. Sarah Palin draws huge crowds and might squeak up to the bottom of the list driving sales with book tours. But this is a woman who ALREADY has platform. What about a tour as a marketing tool for someone with zero platform?
As a new, unknown author I did not pull in Sarah Palin sized lines of readers, hearts thumping to shake my hand. Why would they come? At the best signings I had maybe ten people show up to see me specifically. So this wasn't about getting people to buy my book because it was so awesome that I stopped by.
So if it wasn't about selling books, then what was it about? Well, it was about selling books.
After visiting over 60 book stores in 6 states and doing 11 offical signings, I saw that hand-selling, by booksellers, e.g. "psst Author X is great," CAN make a difference. And so stopping to do driveby signings as well as regular signings, briefly introducing myself to the staff, AND giving a promo copy of the book to the big fantasy reader on staff can make a difference in that store. But it can't be the only method.
As a brand spanking new author you're not trying to move 100,000 copies, although that would be nice. Look at the advance numbers. You're trying to earn out that advance, first of all. Anything above that is gravy. Let's say you get a $6,000 advance and they're going to print it in paperback. They give you a 10% royalty on each book. At $7.99 that's 79 cents per book. Which means you have to sell about 7,500 to earn your advance back.
Let's say you go to 60 book stores. Half of them get turned onto your book and sell 2 extra copies. Hummm. What if they sold four extra copies. Still not a significant change. But what if one book seller goes nuts and sells 20 copies? What if you get 6-10 that do that? Well, it's still a small seed.
This happened to Larry, Dave, & I. At one store in Phoenix we saw a huge display of a fantasy author's books. Why was it there? The fantasy reader on staff loved it and turned the rest of the staff on to it as well. That wasn't the only store. One store put 20+ copies of my book on its octagon (the display right as you enter the doors) because of this. All total, I think the tour itself induced 12-13 stores to order 20+ copies right off the bat (normally they stock only 2-4 of a title). I don't know what the result may be with the other 45+ stores.
Was it worth the cost? I certainly didn't make the cost of the trip back. But it's a seed. I don't know how it might pay off. But this is a business. Like any other business I have to build up my brand. And while it would be nice to start with a huge promo budget, I don't have it. So I have to start where I am. And I try to use a variety of methods to build it. I'm not going to cast all my seeds in one spot of ground. Book tours are one method. I'll do some book tour stuff next year. I wish I could track the effectiveness of the dollars. I can't. But as a new author with a small group of readers, I figure doing something is better than nothing.
[This message has been edited by johnbrown (edited December 27, 2009).]