Personally, my era is the British Isles between 1640 and 1685, but more specifically looking at the English Civil Wars and the political situation during the interregnum.

The book I most enjoyed reading about the time is Free-Born John: A Biography of John Lilburne by Pauline Gregg. It focuses specifically on John Lilburne, the leader of the Levellers movement and general political nuisance, but he was so involved that it really gives a good overview of attitudes and events of the time, but with that personal grounding which I personally really like with my history.

The other two books I'd highly recommend for the era are The English Civil War: A People's History by Diane Purkiss, and God's Fury, England's Fire by Michael Braddick. The first is very people-focused, using contemporary written material to talk about how the common man felt about the situations they were suddenly thrust into. The latter is a much more historical look at the actual events that took place, what caused them, and how they were concluded, but is ultimately an excellent source for factual knowledge.

My area, Australia during the First World War, doesn't have just one book, it has twelve. During the First World War, Charles Bean, the official Australian War Correspondent, kept meticulous records of the actions of Australian forces during the Gallipoli and Western Front campaigns. Bean personally witnessed many of those campaigns and after the war he set about collecting every document pertaining to Australia's role and experiences. Those documents aided Bean when he set to work writing the Official History of Australia in the War of 1914 - 1918. The official history eventually grew to twelve volumes and covered the Australian experience from the declaration of war in 1914 to the armistice. It includes just about every action the Australian Imperial Force was involved in as well as a very detailed context as to why. Bean personally penned six of the volumes himself, those that pertained to actions he witnessed. The rest, covering the Australian involvement in the Middle East, the Australian Flying Corps and the Royal Australian Navy, were penned by additional historians though Bean still played a large part in their creation. Together, the twelve volumes comprise probably the most comprehensive history of any nation during the First World War and are essential reading for any work that pertains to Australia during the First World War.