I saw the BookBook iPhone case at the Apple store in San Francisco, thought it was great but a bit expensive at $59.99 plus tax (about £40). Saw this one on Amazon, apparently made by Boxwave but looked exactly the same, for £17. For £17 it was worth a punt, imagine my surprise when it turned out to be a genuine BookBook, just in a Boxwave box. Has the BookBook logo on the sleeve and everything.
Quality is excellent, just be aware that the box is not as 'beautiful' as the BookBook box (just a plastic sleeve). I bought this for myself so couldn't care less about the box, but if you're buying this as a gift this might be an issue for you.
As with most cases of this type, it's a bit tight for credit cards in the beginning, but loosens up quickly. I also found it awkward to make calls with the phone in the case; not only does it look strange (understatement), but the proximity sensor doesn't work properly; meaning my ear kept either activating the speakerphone or disconnecting the call.
Capacity-wise, the case will take 4 credit cards and a couple of banknotes (folded) quite comfortably; any more and it starts to bulge.
Overall I'm very happy with my Boxwave (BookBook) case/wallet. There are compromises; it's fairly large and bulky, and it's difficult to use your phone as a phone while it's in the case, but as I typically take my phone AND my wallet with me anyway, it's actually a space saver to have both in one. The quality is excellent, and it does attract comments; mostly along the lines of "Why did you bring your bible with you?".
EDIT: I've now had this case for a few months, and the front cover has split. The spine also has horizontal reinforcing 'bars' which have now come loose so the whole thing is now floppy. I don't expect these things to last forever, but a couple of months is a little too short a lifespan for a 60 pound product.