I started reading this book with trepidation. The last Theroux book I read was "Kingdom by the Sea", a book that primarily sought to inform the reader about how smart the author was and how he didn't much like anywhere in England at all. It was with great surprise that I actually thoroughly enjoyed the book from cover to cover.
Theroux is from an academic background and this often shows in his writing. His text is can be ponderous and abstract - examining what it is to be alive and to be in a foreign place. Unlike "Kingdom", however, which was 90% in this style, "Pillars" is a lot more fresh and accessible.
It should also be noted that Theroux's approach to travel is very individualistic - he takes the most pleasure from the most obscure places. He covers Barcelona in one page, Greece in 2, but spends a chapter on a remote village in Tunisia. This is perhaps the essence of his work. He concentrates squarely on the people in the places he visits, rather than the places himself. This stands sharply in contrast with the writings of the other popular travel writer, Bill Bryson, who seeks out the well known places on his travel and gives his forthright opinion of them. Theroux is more the dark shady traveller who mills around the edges of the sites and observes those who are there to see the sites.
Overall, I found the book to be highly enjoyable. It gives great insight into the people and culture of the Mediterranean, but don't expect to use it as a planning book for your next holiday - it is definitely the tale of one man's journey.