You could write a lot of different books with the title The Public Sphere: An Introduction. The concept of the ‘public sphere’ is a metaphor that we use to think about the way that information and ideas circulate in large societies. It's a term in everyday use to describe information when it's made generally available to the public: we say that it's in ‘the public sphere’ (see, for example, Furedi, 2004: 4). But the phrase also has a more precise meaning in academic writing about culture and politics, where it's a central and well-developed concept for thinking about how democratic culture should work. This double existence makes it difficult to decide which kind of Introduction to write about the topic.

You could, for example, write a description of the public sphere as it currently functions in Western democracies (listing the main institutions, how they work, who are the most powerful figures, and so on). Or you could write a book exploring the current debates about the public sphere that are taking place in public culture itself (tracing the ways that television, newspapers, popular writers and public intellectuals are discussing the public sphere within the public sphere). Or you could write a book that traced the academic history of the term ‘public sphere’ (looking only at academic writing on the topic, surveying the most important academic writers and their contributions to academic debates).