If you have a desire to learn anything about econometrics, especially if you've seen some basic information about regression / OLS in a stats class before, this is the place to start. What is learned here is not only the underlying math but also the all important intuition behind the math and the stats and ultimately the econometrics itself. You don't just learn why a formula works, how it is written, and what the proof looks like. The author goes to length to ensure that you also gain a broad appreciation for the assumptions upon which the methods are based, and ultimately what happens when you violate those assumptions. This is a critical part of learning statistics and econometrics, one which is far too often neglected by students, instructors, and authors alike. A key part of any statistical exercise is the intuition behind it, and a working knowledge of how and why the methods chosen are valid. Ramanathan does an excellent job of making sure you understand these ideas every step of the way, throughtout the text. There are plentiful references to earlier sections with related concepts, constantly linking new ideas with those covered in previous sections and chapters. Appendices between chapters also delve into the related mathematics and provide additional proofs for those interested.

I believe there is no better introduction to the subject of econometrics than this work. My instructor required this text in our beginning econometrics course. He never taught directly from the book nor did he assign work from it. We were merely told to purchase it as a requirement for the class so that we would have it as a reference whether we thought we needed it or not. I found myself reading this book constantly, despite never having been required to so much as open it for the class. The book is more than worth it, even at twice the price.