The pecan-pie-topping had something from chiff that got me started thinking about cookbooks that don't work - for you, at least. She mentioned Bittman and the Silver Palate; I've had good luck with Bittman and the first two SP books, but the last one was a no-go.
The biggest no-hitter for me (that I can think of now) was a Russian Cb called Please To the Table. It read really well, and I wanted those recipes to work. But nothing I tried was anything more than merely edible. I had high hopes; those Eastern European cuisines often appeal to me.
So instead of your greatest hits, what were your greatest misses?