This is the book which made Smith's name, and in which he first mentioned the much-misunderstood "Invisible Hand". It's essential reading as an antidote to the "101-ist" perception of Smith as a supporter of unfettered capitalism. It starts from the observation that we all feel sympathy for the suffering of others, and joy in their joy, and explores how society is best ordered to maximise sharing benefits with all.
This was also Smith's last book - he worked on the revised edition until just before his death.
A bonus in this edition, and one worth paying the price of the book for, is Amyrata Sen's introduction, which stands as a better defence of Smith than any amount of backhanded compliments showered on him by the apologists of Wall Street.