Now after that, while it isnt a book, if you want a well told narrative on WW1 then look for Dan Carlin's Hardcore History series "Blueprint for Armageddon". It does a masterful job of telling the WW1 story.

"The Guns of August" bu Barbara Tuchman is the seminal work on the start of the First World War. It covers such a short amount of calendar time, basically 1 month, but it goes into exhaustive detail on the communications & secret alliances that caused the event.

Any history course would always start with that work.