Smiles presents Thrift as a companion to his earlier books Self-Help and Character, arguing that thrift is the basis of both. Thrift, in his definition, is private economy: the wise ordering of one's earnings and household, knowing how to earn, how to spend, and how to save. He frames it as a moral subject rather than a financial one, since the right use of money draws on generosity, honesty, justice, and self-denial.
He opens with industry. Wealth, he argues, comes from labour, is preserved by saving, and grows through diligence, so that it is the savings of individuals that compose the well-being of a nation. Economy, in his account, is not a natural instinct but the growth of experience, example, and forethought, learned only as people grow wise and thoughtful. The thriftless prehistoric man saved nothing, and thrift itself began with civilization, when people first learned to provide for tomorrow as well as today.
Much of the book gathers the practical means of saving and the people who used them: regular accounts, savings banks, penny banks, friendly societies, life assurance, and co-operation among workers. Smiles fills these chapters with examples, from self-taught engineers and artists to ordinary depositors, to show that competence lies within reach of most people if they take the means to secure it. His recurring point is that small sums and small habits, faithfully kept, accumulate into independence.
A central chapter on little things drives this home. Character is built up on little things well and honourably transacted, and neglect of small matters, captured in the careless phrase It will do, ruins fortunes and enterprises. Against the popular faith in good luck, Smiles sets diligence and attention: it is not luck but labour that makes men, and luck whines while labour whistles.
The later chapters turn to the moral dangers Smiles most wants to warn against: living beyond one's means, the worship of appearances, and debt. He attacks the conventionalism of keeping up with others, the snobbery of a false respectability that looks only to outward show, and the misery of those who run into debt to seem rich. The book closes on the art of living, the skill of making the best of one's means and finding happiness in small, common pleasures faithfully enjoyed, so that even a humble lot, ordered with taste and self-control, can be a good one.