The First World War question

WW1
1) John Terrain. The First World War (1965) - short, but quite detailed depiction of all basic operations of WW1 (but nothing more, it is only military side of conflict, for exploring political, economical and other aspects you should read other books).
2) Barbara Tuchman. The Guns of August (c. 1961) - all-time classic, it is a highly detailed depiction and explanation of a summer crisis of 1914 and first weeks of war (until September and first German defeat in France).

WW2
1) B.H. Liddel-Hart. The Second World War (c. 1960's) - British classic work, which unites strategic, tactical and some political aspects of the WW2 in a single volume. Not my favorite, but nevertheless useful to know.
2) W. Shirer. Rise & Fall of Third Reich (1960). I think it is (by date) the best work about WW2 in English by an American author, at least in terms of style. Depicts the late 1930s in Germany and Europe, and also gives a very well-made overview of a basic events of war. Written by an eye-witness of a life in Nazi Germany (Shirer was an American correspondent in Berlin until 1941).
Of course, there's a lot of other great books, but if you want to start with something, I think it will be enough.

I like John Keegan also love war and political history

The Proud Tower: A Portrait of the World Before the War, 1890-1914 also by Barbara W. Tuchman is very revealing about the conditions in Europe prior to the onset of World War I.

Paris 1919: Six Months That Changed the World by Margaret MacMillan is one of the best studies of what happened between WWI and WWII including the consequences echoing late into the 20th century.

Author Rick Atkinsons trilogy of WWII in Europe, The Liberation Trilogy Boxed Set including these three works:

- An Army at Dawn: The War in North Africa, 1942-1943
- The Day of Battle: The War in Sicily and Italy, 1943-1944
- The Guns at Last Light: The War in Western Europe, 1944-1945

is without current equal. I highly recommend Atkinson's work and it includes extensive notes and bibliographies that provide a great resource for additional reading and/or research.

The Economist ran a piece on recent WWI books of note (3/29/14 issue).

Hew Strachan's "The First World War" is an excellent one volume survey. I would also recommend Niall Ferguson's controversial "The Pity of War". Since this year marks the 100th anniversary of the out break of WWI, one could also try Amazon U.K. or any number of British web sites . For World War Two I would still recommend Gerhard Weinberg's, "A World at Arms", which is a one volume (albeit a very large one) global history of WWII. I agree with CD, Rick Atkinson's award winning Liberation Trilogy is not to be missed.

I just finished "A Mad Catastrophe" by Geoffrey Wawro, which deals with the many disasters suffered by the Austro-Hungarian Empire in the first year of the First World War. A very good look at an often-ignored front of the war.

WW1: There's a ridiculous number of solid one volume histories, although these tend to be heavily biased in favor of the country they were published in. I second the Tuchman books (adding The Zimmermann Telegram) and Paris 1919. Massie's Castles of Steel (and the prequel, Dreadnaught) for the naval side (including the Dardanelles campaign), Stevenson's Cataclysm for a crunchy, numbers-heavy look at the home front for the various combatants, Alistair Horne's Verdun for a look at what was probably the most important single battle of the whole war, Mark Thompson's The White War for a look at the Italian front (largely ignored in those single volume histories, which tend to focus on the fighting in Belgium and France) and Fromkin's A Peace to End All Peace for a sketchy overview of the campaigns in the Ottoman Empire and the consequences of the war in the Middle East (really excellent, wish Fromkin would write something similar for each of the fronts).

Looking for: Good histories of the Balkan front, Austro-Hungary (going to give the Wawro book Mike suggested a shot), something on the Russian side of the conflict that isn't written by a Communist/Anticommunist shill.

I'd recommend anything by Lyn McDonald. I read a lot of her book when researching my novel. 'Rose of No Mans Land' probably being my favourite.

Niall Ferguson's 'The War of the World' covers both WWI and WWII, as well as every other conflict (hot or cold) of the 20th century.

I agree with a number of the above comments, about Tuchman and John Keegan. Keegan's First World War had a good overview of the war from a political and military perspective. It talks about where the world stood going into it and what came out of it when it was all said and done.

Everyone will cite Tuchman's 'The Guns Of August' and 'The Proud Tower' for the runup to WW1, but instead I'd go to a fine new book by Margaret MacMillian, 'The War That Ended Peace'.

Do you want to focus on the ETO or the Pacific. Do you want land forces or naval forces?