The Theory of the Growth of the Firm is a classic book in management literature, and one that is explored by academics as well as business enthusiasts. With this book, Penrose founded what's known as the resource-based view. Essentially, she determined that there must be something inside the firm that drives its growth (i.e. success).
The author explores the reasons for such growth. Penrose moves away from the neoclassical economics model of the firm towards a definition of the firm as one that has administrative responsibilities (strategic planning or management) and a view of the firm as a collection of resources (human resources, technologies and other capabilities a firm has). She argues that choice of how those resources are put to use is central to a firms "entrepreneurial" activity.
Penrose goes on to say that change and growth of firms must be driven from inside the firm because the economy as a whole does not constrain firms. Managers, she says, know that they can alter their environment, and that the environment is not independent of their activities.
The resources that are available within firms are ever changing, of course, and often come together in bundles. This means that there are always some resources that are not being used, or being used inefficiently. Managers who realise this can develop those resources and grow their companies as a result. Thus, it is knowledge in combination with resources that drives growth. This is also what makes each firm unique: there are hundreds of ways to combine those resources, and each firm does it differently.
The book then talks about how growth takes place - sometimes as part of a diversification process or through an acquisition or merger. Penrose also discusses the role of time, and the difference between a small or a larger company growing. Growth, she concludes is possible for all firms - size does not necessarily mean that a firm is more efficient (which is the typical economic argument). The only thing that constrains growth, really, is the limited capacity we humans have for managing a lot of change at once.
The style of writing is conversational, if somewhat dated. The only slight drawback is that Penrose often returns to hammer on the same point. But that's not unusual for this type of book. The most astonishing aspect by far is that Edith Penrose was a woman, in a world of business and academia that then, and still now, consists largely of men.