[READER]: Personally, I think that Nicholson's Intermediate Microeconomics book is better than Varian's. Also, Costas Azariadis has a book out on dynamic macroeconomics that is good. Angel de la Fuerza also has a good book on Dynamic Methods in Macroeconomics. (I think that this is the best one from which one can learn the basics. Nothing that Sargent has written on dynamic economics is well-written. The Lucas and Stokey book is confusing for beginners, I think.
Also, there is an old book by E. Klein called Mathematical Methods in Theoretical Economics (or something like that) that is a good general and reference book.
[Mike]: I've always enjoyed Nicholson's Microeconomic Theory: Basic Principles and Extensions. First published in 1972, but has gone through quite a few updates and an 8th edition is currently avaiable. The 6th edition of the book that I own is quite a useful reference. It's written for 2nd and 3rd year undergraduate students, so if you're looking for a book at that level, you can probably purchase an older edition at a used bookshop fairly cheaply.
I've never used his more advanced book Intermediate Microeconomics as the book by Varian has always been the preferred choice at the schools I've attended.
I must admit I'm not at all familar with Intertemporal Macroeconomics by Costas Azariadis though it has gotten awful reviews at Amazon. I've never even heard of the book by de la Fuerza and cannot find any information about it online. What is the full title of the book?
I also find Sargent's material difficult to read, but there's a wealth of knowledge in his writing if you're willing to be patient. The book Recursive Macroeconomic Theory by Ljungqvist and Sargent is one you need to have on your shelf if you want to study Macroeconomics at the Ph.D. level. The Stokey and Lucas book Recursive Methods in Economic Dynamics should only be read by those with a firm understanding of macroeconomics as it is a very advanced book.
I've never used Erwin Klein's Mathematical Methods in Theoretical Economics: Topological and Vector Space Foundations of Equilibrium Analysis. Seeing as it is 30 years old, it might be difficult to find in a local bookstore, but you could always try to find a copy on eBay.
Thank you for your book recommendations.
As I stated in the previous article I'm sure I've also left out more great resources than I've included, so if you know of a useful book in economics, or you would like to ask me a question, please e-mail me using the feedback form.

