I had a number of people ask why I made Demonsouled a free download, and what I hoped to gain from it.
Basically, the Demonsouled is the first in a series, followed by Soul of Tyrants and Soul of Serpents. By making Demonsouled free, I hoped that people would 1.) download it, 2.) read it, and 3.) like it enough to take a chance on the remaining two paid books, along with any subsequent books I will write in the series. And this strategy has worked out rather well – I’ve sold substantially more copies of the second and third book than I did while all three books were paid. (In fact, I’ve sold more copies of Soul of Tyrants than Demonsouled did while it was in print from 2005 to 2007.) In the Internet age, one of the biggest problems writers face is obscurity – how do you get people to take a chance on reading your work? Having a free first book in a series draws attention, while keeping the remaining books non-free offers the opportunity to sell copies (if the readers liked the free book enough, of course).
I don’t think this would work out as well with a stand-alone book. If a free book is part of a series, I suspect if people like the characters and the story enough, they’ll continue to the next books in the series. But in a stand-alone novel, the story wraps up, and it’s a bigger leap to go to a completely different story with different characters.
I could, of course, be entirely wrong, but this is how things have worked out in my experience so far.