Harry--I have The Geek Handbook on my Kobo-1. It is 2.7 (and change) MB in size. No real size difference between the Adobe DRM file and the DRM free one.
Even this seems odd, as it is a very short book (fewer than 60 pages) and a huge book like The Collected Works of William Trevor (1330+ pages) is 2.9 MB.
I looked at all of my files sizes and see that out of 90 books, 10 are 2 MB or more, and only one book is over 3MB--and that is a 250 page novel. I am clueless as to why your version of the book is so much larger.
Re the DRM: You don't ask, I don't tell
.