Of the twin vices of heft and tiny print The Compact Edition of the Oxford English Dictionary has both. I've had my used (two volume) flea market copy of The Compact for over twenty years. The magnifying glass and slipcase were absent when I purchased but back then I could read the tiny text. These days, I default to +2.0 reading glasses and a 100w equivalent lamp though I could probably get by with less...I think.

It would be great to have as an ebook, but such a thing does not exist and if it did, I suspect the price would close to two magnitudes more than the $8 I negotiated for my copy...heft perhaps had the virtue that the seller was less inclined to lug those many pounds back to their car.

Ebooks don't necessarily provide perpetual access: http://www.slate.com/articles/technology/technology/2009/07/... and https://www.theguardian.com/money/2012/oct/22/amazon-wipes-c...