What I like most about these two texts is that they pack so much relevant and clearly presented information into so few pages. Burke follows the course of cultural history as it develops through the convergence of many disciplines. He also provides a handy year by year listing of the most famous examples of the genre. Williams has created a short encyclopedia of cultural "buzz words". He shows where these words originated and how they've changed (sometimes in surprising and even drastic ways) over time and through usage.
If you are intrigued by how the notion of cultural history has evolved in the last century and if you want to see just how strange the course of a word can be as it metamorphoses and winds its way through the centuries, I heartily recommend both books.
Take a gander at 'em over at Google Books!