If you are interested in the naval aspects of WW1 (which are often overshadowed by the trench warfare of the western front) then I highly recommend two books by Robert Massie: Dreadnought, which is about the naval buildup to WW1 and the shift from older battleships to newer all-big-gun ships (named for the first one, HMS Dreadnought), and the sequel Castles of Steel, which is about the actual war.