Depends on what you want really. Is it more the big picture of the war or more details about certain battles or events, persons etc ?
Must admit I am a little bit of a nerd when it comes to this and have a decent ww2 libary. Without knowing what you want I give you (and others a few tips)
By Niklas Zetterling:
http://www.amazon.com/Kursk-1943-Statis ... 169&sr=8-7
This is a statistical overwiev of the battle at Kursk with the preludle to the battle itself and a day by day reference to what happend.
http://www.amazon.com/Normandy-1944-Org ... 361&sr=8-1
About the Normandy campaign and a few new ideas on that campaign
http://www.amazon.com/BISMARCK-Final-Ge ... 361&sr=8-5
About the destiny and story about the Bismark battleship. Quite exciting with a view from both sides even if you know how it went its still to a hold on me at least. Exciting book.
http://www.amazon.com/KORSUN-POCKET-Enc ... 361&sr=8-3
About the Korsun battle also known as the Tjerkassy pocket 44.
WW2 participants:
http://www.amazon.com/Grenadiers-Genera ... 645&sr=8-2
The story of Kurt "Panzer" Meyer the famous and dynamic German comander. A personal favorite of mine (the book)
http://www.amazon.com/Tigers-Mud-Comman ... 852&sr=1-1
One of the Tiger aces of the war and comander of a Tiger company at the Leningrad front (mostly) (Wermact not SS) and his story.
Frrom 44 to the fall of Berlin
http://www.amazon.com/Infantry-Aces-Sol ... 078&sr=1-1
Combat stories of eight German infantry soldiers: one paratrooper, two members of the Waffen-SS, and five members of the Wehrmacht
A concluding chapter examines infantry tactics . Shortter storys from soldiers about 50 pages per soldier. Fun book if you like first hand accounts of infantery men who were nothing short of aces.
Units:
So many books but here is a few I like peronally.
http://www.amazon.com/SS-PANZER-AUFKLAR ... 64&sr=1-10
Class book on the Nordlands (SS The Grenadier division sister div to Wiking if you want), its mostly about the Rec abteilung but covers the units birth and first station in Yougoslavia to the end in Berlin and a few events like a murder on a SS officer in Berlin with a few maps and some good black and white pictures in every chapter.
http://www.amazon.com/German-Elite-Forc ... 059&sr=1-1
The story of 5th Gebergisjäger Div and some good allround info on the Brandenburgers. Shows isignats (spelling) and a few words of the most important people in the Divisions/units.
http://www.amazon.com/Waffen-SS-Elite-F ... 345&sr=1-4
General story of the first 2 SS Div Leibstandarte and Das Reich. More general but a good start and it covers their history but not every battle in detail. Also shows isignas and a few words on the leaders.
http://www.amazon.com/LIONS-CARENTAN-Fa ... =1-1-spell
Fallschirmjager Regiment 6, 1943-1945 . Quite remarkeble book with some never before known info about the regiments participants in Italy 43.
Full appendix on the units organization throughout its excistence and black and white pics and a few maps.
Hopefully something was of use to you or anybody on the forum.
Pardon my english. I am not a native english speaker but hope you all understand what I mean.