Since I last used Zotero a few weeks ago, the book icon has disappeared. I am using Zotero 4.0.20.2 (Mac). I tried looking up the same book on a few different sites, including Amazon, just to make sure it was not a problem specific to my university library's website, but the book icon does not appear on any of them. I also tried resetting translators, but this did not help. I recently updated Firefox to 32.0.3 (Mac); I don't know if this is part of the problem.