Rounding out my tour of classical economics, I've recently read Jean-Baptiste Say's Treatise on Political Economy. I have some regret that I saved this one for last - and have to admit that it's simply a matter of procrastination: a three-volume set whose title led me to expect a lengthy discourse on taxation and government spending in the nineteenth century (which is a good description of the third volume) seemed to be very oblique to economics in the modern era.
The first two volumes, however, were fascinating. Say addresses a number of topics his contemporaries overlooked, and which are particularly germane to the present age: he considers the effect of technology, the value of knowledge-workers, the rationale for customer loyalty, the service economy, the premium paid for brand preference, and many other topics that Adam Smith either ignored or misconstrued - and which the present-day scholar for whom Smith is their only exposure to classical economics continue to ignore and misconstrue.
Say's work is often a footnote in economics textbooks used to train present-day managers, which is perhaps ironic in that it seems far more relevant to the present-day economy that is increasingly based on service and dependent on technology. It should perhaps be the other way around: with Say pushed to the fore and Smith footnoted as his predecessor.