1912 Harpers Edition

Because the Field and Stream serials extended from 1912 into 1913, it is clear that Harpers 1912 edition overlapped the magazine publications.  We don't know the specifics, but it seems obvious that there was some kind of collaboration between the two publishers.  Why?  Because the text is identifical and Harpers "cherry picked" what they felt were they best of Douglas Duer's illustrations.  By the end of 1912, Riders of the Purple Sage was appearing nationwide on best seller lists for the first time in Zane Grey's career.