Totally agree with Michael. I wrote a book once and it took over a year squeezing in time with my full-time job. Assuming you don't want to do the book full-time, it will be an uphill battle.
A middle of the road approach might be to have your business card with a very prominent blogging URL. This will allow you to focus on your business, and have an outlet to communicate your POV on your business and trends that your clients can connect with easily. Maybe an occasional white paper or two when you need a deeper dive than you can accomplish on a blog entry.
It will help you keep your content much more timely and relevant, reach your audience much faster, without being a complete time drain.