Mill is the great synthesis of nineteenth-century economics. The Principles are tedious at times, but provide a generally illuminating account of the ways nineteenth-century citizens reconciled themselves to an increasingly quantified world. Mill engages usefully with most major economic theories of his time, including inheritance rights, speculation, taxation, and the well-being of the working class.
If you're using this edition for a historical or otherwise scholarly project, please be aware that it's based on the 1865, rather than 1848, edition. Some of Mill's revisions are substantial.