Did a search. The book is "Mr. Cornell's Railroad and How It Grew" by John Connell (1982).
An eBay seller still has the same copy with an asking price of $130.55; one sold on eBay in 2008 or 2009 for about $18, I picked it up via a Google search catching part of a feedback comment. Syracuse University has one in their library, I've never taken the time to go look at it - it's one of those books you can only look at in the library, you can't check it out, and while you can get copies made out of it, seems like the library staff has to do it, obviously they're trying to maintain the book in good condition.
I would say if you have the cash, buy a couple copies, put one away, and put it on eBay in a year or two when it's out of print.
I should add I have some track diagrams from old LV blueprints of much of this line; I used to sell them on eBay myself once in a while, but I haven't tried to list any since eBay changed their rules with regard to that sort of material. While by no means complete, a lot of them are drawn to scale. They came out of old LV files I got from a couple of sources; one file even included the report to the ICC seeking abandonment of either Horseheads to Van Etten or Van Etten to East Ithaca. One I don't think I ever copied shows DeRuyter, including the stub of former NY&OM line that remained as a siding there - and labeled as NY&OM.