I have both 2nd and 3rd editions. I am more attracted to reading the second edition cause the paper is thicker and print bolder which is what I like. Plus its smaller and easily can be carried, held and easy on the eyes. I will probably take these to my grave just in case. Thanks Mary for your hard work. She is in wiki if you want to read about this amazing woman mathematician and physics professor. Get this book. The second edition. You wont be sorry.