I'd say Issola is the best (I'm partial to when the series goes off into Epic Fantasy land), but yes, Teckla is definitely the worst. You should not take your own marriage falling apart out on your characters.They're also of a little more varying quality than some other series. Jhereg and Yendi are by far the best, and Teckla is the worst IMO. The rest, and there's quite a few, run the gamut between those highs and lows.