When not to open your wallet:
Both The Tunnel and Der Rote Komet are also already available in German on Gutenberg.org, and can be had in plaintext. I have to wonder if this "translator" (who doesn't profess to have any great skill with German) just intends to snake from Gutenberg, and run a translator.
If you really want something to shake your confidence (from his Indiegogo):
"Once the deadline for this campaign passes, everyone who donates at least $2 will receive a digital copy of The Red Comet in their choice of format: ePub, .Mobi, or PDF, all DRM free (if you need your copy to be in some other format, let me know and I will see what I can do)."
"Currently, I am working on a translation of Der Tunnel (The Tunnel) by Bernhard Kellermann, a novel from 1913. So for the backers who purchase one of the further tiers, this would be the second novel you will receive. I do not know when it, or any other novel, will be completely translated and delivered."
The book listed in tier after Der Rote Comet is one he's already got for sale (the Japanese fairytales translation sold as an ebook with no reviews on B&N and the one four star review on Amazon is written by a person who wrote one review), but you have no promise of receipt. You may get a digital copy of the one book, but nothing else - so I wouldn't bother pursuing it.