Three books are eventually planned: The Player's Handbook, The Gamemaster's Handbook, and The Spellcaster's Handbook.
Currently The Player's Handbook is available, a 90-page book containing all the core rules you need to play, and giving a flavor of the setting. To get your digital copy, pay whatever you want. If there are later releases, you'll get access to those as well -- but that said, I have sort of put this aside for now.
See also the text game Skycrawl, set in the same world (roughly) as Dungeons & Drapers, only without all that blacksmith and tailor stuff.