buying books seems to be a personal preference and intended use. I have all the Anatomy of Ship series books and these are not the type of book you sit down and read like a story. They are strictly a reference book, in this case a PDF is far more useful. Taking a quick look at the books i have none of them are really a book you would sit down and read page by page cover to cover like say a mystery novel. Actually once you know who did it you usually don't start from page one and read the book again.
The books in my collection are not like manuals with step by step instructions so there is no need to have the book on my workbench.
As an example last week i wanted information on waterways and building up the bulkwards on a ship. I sat down a flipped through different books and learned ok this is how it was done on schooners, on war ships, on clipper ships in the 1700s and in the 1800s etc. Now i know so armed with information i can go to my work area and design and build, no need for an open book on the bench.
Anothe oddity i started my library back in the early 1970s and by the time i stopped adding books i have over 100. couple years ago i go interested in naval steam ships and decided to design and build the engine room of the steam frigate Mississippi. going to my personal library of 100+ books and years of collecting and i don't even know how much money invested there was nothing, zero, zip not a single bit of information. I got 100 times more information on line and now i have a PDF library of marine steam engines, history of steam, construction of a hull for steam,
keep in mind this post is from someone who does not sit down and read a book word for word page by page, i speed read and scan through a book looking for information and only information i do not care at all the "feel" of holding a book or turning pages. Book are nothing more than a tool to achieve an end result, the faster and quicker i can get the information i need the better things are. Now i wonder once you learn the information and you know "who done it" the book becomes obsolete.