No book can get written faster unless you write everyday. My philosophy is 'if I write more today I can write more tomorrow'. Set yourself up for success by continuing with what you set out to do. The story is worth writing. Work to make it worth publishing.
Now, what does it take to finish a book? It won't be done overnight,that's for sure. But, everyday you can progress to the 'finish line.'
It is extraordinarily crucial to organize your plot and character developments before diving in.
Nothing will hurt the writer more than writing himself into a poorly planned book. But, for the unique few, it helps get over the dreaded Rough Draft. Which leads into my next point...
Once the first draft is written, it may seem like all the hard work is done. WRONG. Finishing a book, and finishing it properly, means you re-rewrite and re-rewrite some more, until you find that you have polished it to the best of your abilities. Not to mention, the best to your taste as well. Don't be mistaken...a book should be good on your standards, but it should also be 'readable' if you plan to have it published.
Plan to write everyday. Make daily goals. Obsess over it. Breath it. A book can't be done with less than 100% effort. By doing this, you're dedicating your technical writing skills. It's the ultimate way to improve your writing. You would be surprised how much it helps!
A story without the love of an author is destined to be a crappy story. Clear, cut, and simple. Emotional commitment to your writing does wonders to the growth of your story. It proves to yourself how determined you are to finish this book.
If this list sounds easy to you, then I don't know what you're still doing here. Write. Write. Write!