A commenter on my Wealth of Nations Book I post asked if I knew of any helpful commentaries or historical overviews. A while back I found A History of Economic Theory and Method by Ekelund and Hebert for $3 on a clearance rack. It is a textbook designed to be a systematic approach to building the history of economic thought. It details the Physiocrats that Smith drew from, and has one chapter on what they believe are Smith's unique contributions.
Much of their focus is on Book I, explaining Smith's labor theory of value and trying to flesh out his various thoughts on capital accumulation. They claim that most economists have never attempted reading WoN, surprise surprise.
From an aside in their text, I learned that when Smith retired from his teaching post he became a customs official for several years, responsible for implementing the tariffs and quotas on trade which he railed against. Apparently he did his duty well, putting duty and self-interest above his own beliefs (ie: he didn't try to sabotage the welfare-harming customs system). Interesting.
I'm reading WoN on my Kindle DX, which I no longer have buyer's remorse about. It has greatly sped up my reading time and it allows me to highlight and make notes. Those are archived on my Amazon website, which allows me to easily turn them into essay questions and blog posts.