How else would I do a firmware update of my books? I wouldn't want to trust wifi for such a large collection. ;)

Seriously though, the real answer is that fiber internet comes into the house on the far left side of the library wall, which also makes a decent place to keep the router so that wifi can reach all of the front upstairs of the house.

Directly beneath this room is a room that we use an a home office. When I moved in there was an old phone jack on the far right side of the wall with a cut phone cable running down to the office. I pulled that and replaced it with Ethernet to the office, and then also from there put in runs to the den for the TV/media setup and the back of the house for wifi extender backhaul.

Back to the bookshelf, I don't know what I'm going to find when I pull the trim to do the install, as this is a 120 year old house. By adding the conduit I can hide the Ethernet run across the room in the base if it won't be an easy run through the wall. Also by going with conduit I can easily upgrade it in the future with fiber or whatever if/when CAT6 isn't enough. I'm going to put a lower door on the left and right most bookcase sections so that I can hide the networking equipment in the left and whatever else in the right.