I just read about this on Simon Rogers’ LiveJournal blog:
All of our GUMSHOE PDF products are on sale over at rpgnow.com at a 15% discount until 19th March. Our average rating over 22 reviews is over 4 out of 5. So that’s Trail of Cthulhu, Mutant City Blues, Esoterrorists and Fear Itself. Get them while you can!
I just LOVE the GUMSHOE System, and so I took the opportunity to get the Esoterror Fact Book for just $12.71! If you haven’t done so, you should at least consider getting the core rulebooks for Esoterrorists, Trail of Cthulhu and Mutant City Blues. They are definitely worth it!