Kirkus Reviews gives Um... a starred review!

It's a "A lascinating fook at yet another revealing instance of human imperfection."

The review also says:

Perhaps the most interesting chapter is “A Brief History of ‘Um’.” The author perused books on public speaking all the way back to Aristotle and found no condemnations of “um” and its dilatory relatives until fairly recently; he believes radio’s advent in the 1920s prepared the way for our current insistence on verbal perfection.