I did a Ph.D. in English and neo-Latin poetry, and we have a library full of books with everything from the classics to mystery novels to trashy fantasy-sci-fi books. When we bought the Lodge, our realtor told us to get rid of the books because they scared potential buyers. "We haven't even closed yet, and already you're planning to sell the place for us."
"It never hurts to plan ahead," the realtor muttered darkly. "Books look cluttered."
We ignored her; she was also bitter about the fact that we wouldn't consider buying places where our 1914 antique Steinway 7-ft grand wouldn't fit. "You could have got that place for a song, but your damn piano wouldn't fit!"
However, we've stayed in B&Bs where there were books in our room, and I agree with posters above that this contributes to clutter. Besides, you have to dust the damn things when you turn the room. We have a nice library where most of the popular stuff--including the trashy vampire and werewolf stuff--is on shelves (I figure skiers and mountain climbers aren't going to be that interested in Herodotus). Guests can build a roaring fire and curl up on one of the sofas.
In the alcove off the sitting room in the dining lodge, we have a variety of mountain climbing books, hiking books, maps, trail guides to our area, Colorado gazetteers, and other "of local interest" books. We also regularly photocopy pages from books so our guests have good maps of the areas for hiking, biking, and back-country skiing.
No books in the rooms, though.