My advice is two fold.

One - go and buy a copy of Traction - http://www.amazon.com/Traction-Startup-Achieve-Explosive-Customer/dp/1591848369/ref=sr_1_2?ie=UTF8&qid=1455378892&sr=8-2&keywords=traction

The book lists 19 channels to help promote your book and goes in depth offering great examples.

Two - my own piece of advise, consider this a distilled version of what Traction says :)

1. Start writing on Medium - offer pieces from your book and get people to "taste" your book.
2. Start a free course and talk about the same things you have written about in your book - you could scale this to paid courses if you get going and are interested in such revenues.

These courses could be in two form - 1. Recorded videos and tools (could be checklists, templates, or anything else that really helps someone) put together into an eLearning course. You could deploy this course on Udemy and watch people jump on it. 2. Live webinars where you engage with your audience - this even helps in refining your book, if you may.