What are some good Unix application developer books?

Thanks.

Thanks Tom,
The advanced keyword scares me, i am a newbie for Unix development. I will also read your advanced suggestion. But what is a good Unix developer book for novices?

I do not do much Unix programming, but despite the 'Advanced' in the name, it was easy to follow when I started out. If you know the C subset of C++ well enough to follow the code I do not think there will be a problem. But you can search for recommended books and reviews here.