I always have to recommend Mother Earth, Mother Board by Neal Stephenson[1] if the thought of undersea cables sounds at all interesting. I'll also second andyjohnson0's recommendation of The Victorian Internet[2] - it blew my mind how much of modern digital culture existed on telegraphs prior to voice.

[1] https://www.wired.com/1996/12/ffglass/

[2] https://news.ycombinator.com/item?id=46433901