I have many books on CD, but have really lost track of what I have and where they are... as a result, they are seldom used, .
I think it may be best to go "old school" and on top of that, I guess it is not high gloss Photo paper that is needed.... Buyers will want the info, not the layout ...
As Rick used to say.... Paper is really the only way to go...
I would think along the lines of 2 large telephone book sized/Type volumes... maybe not as optically pleasing as a 5 volume bound leather set, but praticle and cheap to print.... and go EXPENSIVE... you are not selling the book quality, but the reseach put into it.... The market may be limited, but there would be a group of people willing to pay the price....