Do you prefer hardcover, softcover, or electronic books? What are the benefits of your preference?
I like hardcover the most for its tactile properties and the satisfaction I get seeing it on my shelf. A thick softcover can serve the same purpose, though most of the softcovers I have are shorter, flimsier books that have a hard time staying open on a page. But as I get more books, I find myself gravitating more to electronic copies. In my earlier campaigns I made sure to bring every book I would need for a session, which meant I was limited by the number of books I could carry to our FLGS and how many I could fit on the table at once. Electronic copies remove that limit.
I think the biggest advantage of electronic over physical is searching, especially multi-book searching. I don’t have to review five tables of contents to find out which Monster Manual has the moonrat (it is, of course, Monster Manual 2: the Book of Goofy Ideas), and I can quickly find everything that deals lightning damage if I’m looking for something that fits my theme. But I don’t have a PDF reader that allows easy tabbing, and rulebooks are all but designed to have you flipping back and forth between pages at the opposite ends of the book to understand something. Until I have a program that lets me view PDFs, see my table of contents and bookmarks at the same time, and split my view so I can see two pages at once, a physical copy is just more convenient when I’m doing a deep dive.