The new paperback version of Perfumes: The Guide by Luca Turin and Tania Sanchez is now available under the name Perfumes: The A-Z Guide. The retail price is $20; Amazon has it at the moment for $13.60.
The book includes the reviews from the hardback plus the reviews from the three quarterly updates, and a handful of new reviews and a few other changes. There's also a new index and more FAQs.
The skinny from Tania Sanchez: if you bought the hardback and the quarterly updates, the paperback might not be worth it unless you want everything in one place with an index, or unless you're dying to know their take on the new versions of the Dior classics and/or Chanel no. 5 in extrait (plus a few new reviews that were left out of the quarterly updates). If you bought the hardback but not the quarterly updates, you'd be getting around 450 new reviews by buying the paperback.
Update: after this article was posted, I received a free copy of Perfumes: The A-Z Guide from the publisher. And I kept it.