So you wrote a highly-successful trilogy. Congratulations! What now? Well, you could write a sequel trilogy: new narrator, same old world and intrigue. Some writers want to milk the cash cow for all it's worth. Other writers, like Jacqueline Carey, create worlds compelling enough to justify returning to them time and again. Sinking into Kushiel's Scion is like having an old friend come to visit: all the things that you remember are there, but…