I set the pomodoro timer for 25 minutes, and repeated three times, with the appropriate number of breaks. I've done this several days in a row. I don't seem to want to write for 100 minutes, but that is fine. I am getting a lot done, working for 50 minutes on a chapter on Lorca and postmodern kitsch, and then another 25 on the preface and the order and titles of the chapters. By working on the preface, I am able to keep my attention on the project as a whole, especially as I rewrite the dreaded summary of chapters. For the reader, this summary has the function of "signposting" the contents of the entire book. For the writer, it has a similar function: I am able to see the project whole in one coherent set of about 11 paragraphs, and work out kinks in continuity.
Remember I am working to finish the book by January 2013. I will have ample time if I keep up this modest pace.