Maybe you don't want to buy the book, but you want to support one or more of the creators.
Or maybe you want to support indie comics.
Or you're just a lovely person.
This is the option for you. You'll get added to the thanks list in the trade, and you'll receive our eternal gratitude. Literally eternal, in the year 81652, when the human race has evolved into floating telepathic brains who eat the breeze and poop ice cubes, our ghosts will haunt the ruins of the world and we'll STILL be grateful.
Want to read Slashermania on your personal electronic reading device? Don't want to bother with postage? Released the same day as the TPB version, but without any of that dated actual-possession-of-physical-objects stuff your Grandparents insist upon. Luddites!