How do you decide what kind of book to write?

Now, I am assuming that if you are here, you are starting from scratch. So we must begin at the beginning. What shelf in the bookstore would you find your soon-to-be book? Probably nestled beside the books you like to read. Write what you want to read! After all, you are going to be reading it everyday! Now, some of you will know exactly what they have in mind, but the rest of you, like me, will find yourselves in even worse a fix! You like LOTS of books! Oh, you lucky gourmets! It may take a bit longer, but your possibilities are endless. Here's what you need to do:
1) Go find six or so of your all-time favorite books.
2) Get a sheet of paper and a cup of something delicious and find a comfy seat.
3) For each book, write down what it is that you love. Use the following choices: The story, the characters, or the feeling the book gives you. You may wind up with something like this: The Da Vinci Code: the story; The Pilot's Wife: the characters; and Stardust: the feeling. In short, a high action suspense book with poignant female characters in a fantasy world.
4) Think of this as a treasure hunt. What do your favorite books have in common? What makes them different? Is there a type of situation that you enjoy seeing characters get into? What do you really hate to read about? Write it all down.
5) Imagine you are in an enchanted library and you have just found the perfect book. It was written just for you. What is it about? This is your book. And I'm going to help you write it!