Theory of Functions of a Real Variable

When asked about the best book on analysis, my much older research colleague who went through a traditional, rigorous training in the 60's immediately mentioned the name Natanson. I'm glad I got this book. It's refreshing to read a mathematics book written half a century ago. People then knew how to write and wrote for a clear-minded audience. The presentation is succinct but not abstruse (unlike Hardy's book on Inequalities). I found the exercises at the end of each chapter to be quite difficult.