I read it( first edition) as a first year under-graduate student in the Presidency College, University of Calcutta,India, many years ago.
It was fantastic, to go through it, using mathematical approach, which makes everything so easy to understand.
It has helped me to read easily the Paul Samuelson's Foundations of Economic Analysis, which is a classic on its own.
Now, in its latest edition, it is still a classic, which I use for my undergraduate and sometime post graduate students in Japan. They love it.
If you read it as text, you can sail through any journals of economics without much difficulties.
If there is a Nobel prize for text books, Henderson & Quandt should get it.