Bundle of Holding. A 10% discount on anything bought through the Frog God Games website -- including physical books (although the 10% discount doesn't apply to the shipping, just the books you buy).
Depending on what you buy, that could almost pay for the cost of the bundle right there.
We also added a pdf copy of Cyclopean Deeps #1. That is clearly a gateway-drug kind of thing, so, yeah. It's intended to suck you into buying the rest of the series as it comes out. I am currently working on #6 out of 12.