Full version at the moment has 15 playable characters, 26 classes, 190 spells, 201 items, 67 enemies, 40+ towns/dungeons, and a level cap of 500 (you don’t learn spells or unlock classes past 99, but it’s there because why not). The final dungeon, where you beat the game, will probably be around 20 floors. Possibly more.
Unfortunately, due to software limitations, the game will not be available via Mac or Linux. If you would like to try, however, your options include dual-booting, BootCamp, Parallels, Crossover, WINE, and VirtualBox. Winebottler might also be an option to look into.
An early demo was available as of August 1st. A number of changes have happened since then, primarily adding/changing levels and quality-of-life tune-ups.