Underhill Genealogy Volumes Online
Courtesy of the Allen County Public Library
It appears that the 4 separate digitized versions of the Underhill Genealogy Vols. 1, 2, 3, and 4 are now available to download at the Internet Archive site, courtesy of the Allen County Public Library. There are several formats for which you can choose any to download, though the PDF is the recommended format for your desktop/laptop computer. They were added to the Internet Archive in 2019.
The initial selection displays several reports in addition to the genealogy volumes.
Selecting only "1932" reduces the selections to just the genealogy volumes and an additional reference about Captain John Underhill.