I've read a couple of books on Aztec culture over time. I thought I'd post some recommendations:

Introductions
  • The Aztecs, Richard F. Townsend, Thames & Hudson
    This is a fantastic introduction. The book covers all important aspects about the Aztec empire, culture, history and the conquest. Townsend manages to concentrate the most important facts into relatively little space.
    As I wrote above this is a great introduction and if you plan to read only one book about the Aztecs, go for this one. It has a number of nice illustrations and photographs (unfortunately only in b/w) and even recommendations for further reading on several aspects of Aztec culture.
  • The Aztecs, Michael E. Smith, Blackwell Publishing
    Another "general" book, although this one is a bit unusual. In contrast to most other books Smith does not focus only on Tenochtitlan and the Aztec empire. A large part of the book deals with rural life and describes rural sites excavated by the author. A great book, but I would recommend to read some other book first.
  • Aztecs, Royal Academy of Arts
    This is the catalogue of the 2003 Aztec exhibition in London, Berlin and Bonn. This book is a must! The first part contains articles by different authors on various subjects of Aztec culture. The second part consists of top quality photographs of each piece of the exhibition with a description and analysis for every object. Unlike in most other books, all photographs are in full color. No other book I know can compete with the photographs in this book, not even Aztec Art by Esther Pasztory (see below). There's also a German edition (Azteken, Dumont Verlag).


"Further Reading"
  • Daily Life of the Aztecs, Jacques Soustelle ,Weidenfeld & Nicolson
    Title says it all. Covers every aspect about Aztec life. Highly recommended.
  • Aztec Art, Esther Pasztory, University of OklahomaPress
    The definitive book on Aztec art. Loads of photographs (mostly in b/w, but there are a couple of color plates) detailed description and analysis of the objects, explanations of designs etc. The book is very well written and despite being very thorough it is still very readable. Highly recommended.
  • Turquoise Mosaics from Mexico, Colin McEwan & Andrew Middleton, British Museum Press
    I love this book! The authors examine several of the extant Aztec/Mixtec turquoise mosaics. The book covers materials used, methods of construction and a detailed analysis of each object. If you're (like me) fascinated by the craftsmanship of Aztec turquoise mosaics then you've got to read this.
  • Aztec Warfare, Ross Hassig, University of Oklahoma Press
    This book deals with everything related to warfare: weapons, strategies, politics etc. The second part of the book deals with imperial expansion and describes in detail the conquests and wars of each individual ruler.
  • The Conquest of Mexico, Hugh Thomas
    A very thorough and well researched account of the conquest. Thomas goes into very great detail and even covers things like life conditions in 16th century Spain and the motivations of the conquistadores to seek fortune in the new world.
    There's also a German edition (which I have read) (Die Eroberung Mexikos. Cortes und Montezuma, Fischer Verlag). The translation is very good but the book contains so many spelling mistakes that I was annoyed at times.
  • Aztec Thought and Culture: A Study of the Ancient Nahuatl Mind, Miguel Leon-Portilla, University of Oklahoma Press
    Deals with religion, philosophy and poetry. I like this one a lot, especially for describing religious concepts in detail, something that is sadly lacking in other books.
  • The Sounds and Colors of Power, Dorothy Hosler, MIT Press
    This book is about metalworking in western Mexico (the Aztecs' neighbours and enemies). The book focuses on copper and bronze (gold and silver are unfortunately not discussed). It covers history of metalworking, the use of different alloys, manufacturing techniques. It includes analysis of several artefacts and (very interesting) deals with the question of why metal was used for certain items (bells, needles, etc.) but not for others.
    Not exactly about the Aztecs but I'm including it here because the Aztecs also used copper and bronze and manufacturing techniques were probably the same.


Codices, first hand accounts, etc.
  • The Codex Mendoza, Frances F. Berdan & Patricia Rieff Anawalt, University of California Press
    A post-conquest codex (= an Aztec "picture writing" book), dating from about 1540. The Codex consists of three parts: the first parts is about Aztec history. Part two is a tribute list, listing the various items and amounts that each province of the Aztec empire had to pay as tribute on a regular basis. The third part deals with daily life. The book contains very detailed descriptions and analysis of each page of the codex.
    There are two editions of this codex:
    The one I've got is called "The Essential Codex Mendoza" and is a one volume paperback edition. The codex itself is unfortunately reprinted in b/w in this edition, but there are at least a couple of sample pages in full color so one can imagine what the "original" codex looks like.
    The other edition is a four volume hardcover set that contains the b/w reprint of the codex and all descriptions and text of the paperback volume. It additionally contains a reprint of the codex in full color plus one volume with various articles. I would like to have this edition very much, but unfortunately it is a little pricey (~$500).
    Very highly recommended.
  • The Codex Borgia: A Full-Color Restoration of the Ancient Mexican Manuscript, Gisele Diaz & Alan Rodgers, Dover Publications
    An Aztec/Mixtec pre-conquest ritual almanac, a book that was used for divination. As the title implies this is not a reprint of the original codex. The book contains a reconstruction, i.e. a redrawing of the original codex. Given it's age the original is damaged in various places and the authors attempted to reconstruct missing and damaged areas as well as possible. The redrawing doesn't quite reach the artistic quality of the original drawings (at least in my opinion), but is still very well done. The drawings are accompanied of by a very interesting analysis and interpretation.
  • The History of the Indies of New Spain, Diego Duran, translated by Doris Heyden, University of Oklahoma Press
    Diego Duran was a Spanish friar that lived in 16th century Mexico. He was very interested in Aztec history and culture and with the help of native informants he gathered and wrote down as much information as possible. His writings are one of the most important sources on the Aztecs. Throughout the text there are lots of very helpful and informative annotations by Doris Heyden.
    There's also a second book by Diego Duran dealing with religion and rituals (Book of the Gods, Rites and the Ancient Calendar) but unfortunately that one has been out of print for decades.
  • The Account of Bernal Diaz del Castillo
    Bernal Diaz del Castillo was a Spanish conquistador and member of Cortes' army. He wrote an account of the conquest of Mexico. A very important first hand account of the events that took place during the conquest. There's probably not one book about the Aztecs that does not cite his account.
    I've read the German edition (Die Eroberung von Mexiko, Insel Verlag), which is not so good. Unfortunately there are no annotations by the translator/editor and no commentary. Moreover, the account has been shortened in some places. I've got to get one of the various English editions one day.
  • Cortes' letters
    Cortes' own account of the conquest, consisting of five letters he wrote to Charles the 5th, king of Spain. I read the German edition (Die Eroberung Mexicos: Drei Berichte an Kaiser Karl V, Insel Verlag), which unfortunately only contains only three of the letters. I will diefinitely get the English edition (Letters from Mexico, Yale University Press) since it contains all the letters plus annotations (which the German edition also lacks).
  • Sterbende Götter und Christliche Heilsbotschaft (Dying Gods and Christian Gospel), translated by Walter Lehmann, Kohlhammer Verlag
    This is the transcript of a conversation in 1524 between Aztec nobles and the first 12 Spanish friars that had come to Mexico. The friars confront the Aztec nobles and accuse them believing in false gods and worshipping the devil. Unfortunately only a small part of the original manuscript survived, but this is still a very interesting read. The book contains the text in Spanish, Nahuatl and German as well as an introduction and annotations. The only edition that was ever published is from 1949 and of course out of print. I was lucky and managed to get a used copy.
    There is no English edition of this book but I'm still including it here as I found it very fascinating and "Aztec Thought and Culture" Miguel Leon-Portilla contains several references to it. If you're interested in this one and don't speak German, get Leon-Portillas book.