As Yoda says, “Difficult to see the future is.” But difficult is not impossible. Causes have effects, and the more you have a sense of the rhythms of the past, the better you can sense the future.If it takes you two years to write a book, you owe it to yourself to ask, “What kinds of books will be popular in two years?” Reader preferences change over time, but sometimes they change rapidly. If you don’t keep up, you may get stuck writing a book people no longer want to read.So, how can you de...