Sketchbook found in used book

Over at Fecal Face, Mel Kadel and Travis Millard show off an amazing book published in 1913 that they picked out of flea market trash. When they opened The Conspiracy, they found a big surprise inside. Oddly, the first twelve pages were printed with text and the rest is blank, except for several dozen excellent ink drawings by an unknown Chicago man who previously owned the book.
Link (Thanks, Lindsay Tiemeyer!)