It should go without saying, that if you haven't already read
Locke & Key Volume 1: Welcome to Lovecraft HC and
Locke & Key Volume 2: Head Games HC then you must before purchasing this.
Volume 3 faultless continues Hill's story and Rodriguez' amazing complimentary artwork about the Locke family, and the happenings around the Keyhouse. I'm not going to spoil it all for you - if you've got to volume 3, I'm guessing you already know what all this is about - suffice to say - the story is still flawless quality.
The hardcover edition of this is again beautiful, with the stock picture not doing it the justice it deserves.
There are again the sketches of parts of the Keyhouse, and another great introduction, this time from Brian Vaughan. The hardcover price is only £1 or so more expensive than the paperback, so for an edition that you're going to want to read repeatedly (trust me on this) treat yourself to something aesthetically beautiful *and* more robust, as the hardcover edition undoubtedly is.
I can't wait for my volume 4 to arrive. If you do like Locke and Key and you haven't already tried
CHEW Omnivore Edition Volume 1 HC then it's well worth a purchase.