Tons
Every time I'm at my library, I don't stray too far from the section that has all those WWII/Naval books
I've read Clay Blair's book(s), too.
I've heard a criticism of him being rather anti-German, and on some points I do agree with it. That or he's VERY keen on pointing out all possible German weaknesses, inaccuracies, mis-reports and failures. I haven't gotten to his book on the American subs in the pacific, but if the intro to Hitler's Uboat War is any indication - it should be the reverse. One wouldn't be surprised, of course, given his background. (Of course, I'm not saying that anyone should glorify the German war effort OR that the U-boat war was anything but a failure - but I wish he were a little less biting.)
That said, for being "stupidly detailed" as someone called it - this one's not one to miss. Definitely a damn well-researched book, you can't beat it for the sheer amount of information!