As more episodes are released, the first episode goes free to entire new players into getting their feet wet in the series and then buying the rest of it. (toucharcade.com)
It's a quick and easy way to find new readers and if they like your book, they'll gladly buy the rest in the series. (buildbookbuzz.com)
I'd just bring enough for your flight and first day, and then buy the rest when you get there. (havebabywilltravel.com)