What's the easiest way to legally protect my business?

So wise to recognize that your energies are better spent creating your content than handling the details of protecting it. Leave the "protecting" to the professionals (attorneys).

You don't need to form an S Corporation or LLC to file for copyright protection--you can do that under your own name. However, without knowing what you've created and how you intend to use it, it's hard to say what your first steps should be and what would make financial sense.

A website alone won't protect your IP, nor will the book necessarily protect anything that's not contained in it. Your best step would be to consult with a local IP attorney. That way, you can develop a sound strategy, time frame and budget for protecting your creative work the right way.