Really it depends on what you want. A technical history is really good in the Jentz books, DW to Tiger I, VK 45 to Tiger II, and the combat tactics. The Achtung Panzer Vol is good as well. As far as tiger unit histories go, JJ Fedorowicz publishes a whole slew of them, Tigers in Combat I and II (now available in softcover from Stackpole but the hardcover has much better picture clarity and the color plates are 100 times better.) Michael Wittmann and the Tiger Commanders of the Liebstandarte is good, good pictures and text, but has been criticized as being slight apologetic to the Nazis (this book was written by Patrick Agte who also did a similar book on Jochen Pieper and he did gloss over some of the nastier parts of the story but still they are solid references) Das Reich tigers by schnieder is good, but the pictures are nothing to write home about, the have all been seen elswhere. Combat history of the S.Pz.Abt 503, 507,and 508 are excellent, esp the one on 507. Funklenkpanzer is also a good book although not strictly on tigers it give excellent coverage to the units that used radio control equipment from a tiger. Personal memoirs are hard to find, the most notable being Tigers in the mud by otto carius, which is a good book, but gets a little thick at times. Schiffer published a few books by ex tiger crewmen the first being by rubbel from 503 in the "tiger Project" series but i wasnt too impressed.
PHIL