I learned in school that it was the assassination which started the war, but aside from a vague explanation that nations started lining up behind their allies and then everyone fought, I never quite understood how one lead to the other. Do you know of a good book which explains this well?
Aside from the Bolshevik Revolution, I don't know much about the era. I am sure there are plenty 'o books about the "Great World War", but I couldn't name any, sorry.