This is an impressive and engaging summary of the lives and ideas of the major economists from Adam Smith through Joseph Schumpeter, covering both the people you would expect (Ricardo, Keynes) and some people you would not.
Heilbroner is a refreshing guide because he both has a historical sense of economics and he is not a free market nazi. Moreover, as he makes clear in the final chapter, he shares my doubts about economics as a Science.
Now, I can't speak to how thoroughly he captures all of these authors' ideas - though he does an excellent job with the brief biographies - as I have not read all of them, and the one's I did read, I read approximately a decade ago, but I must say that I think I trust his interpretations and he presents all these ideas in about as easily digestible a format as you are going to find (certainly more so than a boring textbook).
I would strongly recommend this as an introduction to economic history and theory to anyone, including people whose introduction has been one or two university level courses (which no doubt ignored the history, at least that's my experience).
Well worth reading.