Found here. I don’t think that they’re part of the $300 The New Age tier in the Delta Green Kickstarter; I got the impression at the time that the tier in question covered all the hardcover books that Arc Dream’s supposed to be publishing. That was and is a good deal, in my opinion, and I assume that these are print-on-demand softcovers that seem to be becoming pretty popular in the gaming world. PDFs are nice, but so are physical books.
So, if you’re a completist, check ’em out. Alas, I have to budget for that sort of thing these days. Then again, I did get the PDFs as part of my backing, so I’m hardly hurting for new stuff to read.