Computer Networks - A Top Down Approach by Kurose Ross gives a very good overview of computer networks and dives deep into each of the layers of the networking stack.
I found that reddit has grown some very nice communities around topics I care about. As long as I try just a little bit to avoid the distractions that other subreddits bring, it gives great value.
Some subreddits I joined are
r/compsci
r/linux
r/programminglanguages