"Tank Warfare in the Eastern Front 1941-1942", by Robert Forczyk. It covers all the major (and not so major) armoured operations in the East Front during 1941-1942. Great reading, imho.
The so called "Liberation Trilogy", by Rick Atkinson (who won a Pulitzer Prize) is the most entertaining account of the War in the West Front I have ever read. It goes from the foxhole point of view to the highest strategy. All told in a very easy to read and enjoyable way. There are no great theories in the books, but it is GREAT reading. It relates the events going from Operation Torch and the NA campaign (first book) to Italy (second book) and Overlord to the very end of the war in Europe (third book).
"Berlin: The downfall, 1945" by Anthony Beevor. I think it is a must read. Dramatic and, to a certain extent, epic book. Especially since it relates some aspects of whta happened in East Prussia in 1945 which werent well known in west europe (except Germany) until two or three decades.
PS. Oh, I almost forgot: "D Day Through german eyes" (there are two short books). Each book contains 12 interviews of german soldiers which were in Normandy in 6th June and what happened to them. Each interview takes around 30/45 minutes to read. I have to say that they seem to be real histories, not some of the half fantastic stuff you find in other books. The interviews were made by the granfather of the "author" of the book, who was a journalist for a werhmatch magazine and was in Normandy one month before Overlord making interviews to soldiers. After the war, he decided to record (interview) what had happened to those same soldiers (the ones still alive and the ones he could find). However, he never published the material, but his grandson has done it.
These two books give a very interesting point of view (the german soldier one) especially regarding two things: One is why the germans fought by that point and what they thought about the war, even with the retrospective they had when the interviews in the book were made (they were done in 1954). The other thing is the german soldiers who were captured and taken to the beaches and their wonder due to NOT seeing on the beaches a particular piece of "equipment" they used a lot and which has provoked lots of heated arguments in these forums. I will let you to guess what it is.
By the way, both books are really cheap. Just 4 euros, each, at Amazon, iirc.