I would go along with Gary's explanation. Here in the UK if you say 'I think you are a (right/real) piece of work' it means 'I think you are an unpleasant/nasty person.' If you say this to someone then they are not going to be very pleased, so perhaps it would be best to avoid this particular phrase.

I think that it gets used in a few ways, but it is usually quite negative. I would take it to mean someone is rather unpleasant, and who has poor morals. I would use it very carefully - probably only to a very good friend to tease them. If you said it to someone that it really applied to, they would be very likely to do something very unpleasant to you.

It means that "you are a bit weird or unusual" . You wouldn't say it to someone unless they were a very good friend who would understand you were really joking. You could use it to describe someone else and mean it as them being weird. "That Bill is quite a piece of work. He does the strangest things."

根据上面几位的解释和词典意思，汉语可以翻译为，‘我觉得，你真是极品！’，同样需要小心使用。Generally used as a sarcastic "compliment." Reference： http://www.urbandictionary.com/define.php?term=piece%20of%20work http://www.thefreedictionary.com/piece+of+work

You are just complicated.