Richard Ridley offers up his advice on CreateSpace:
His advice starts off interesting, but then swerves into the pond (so to speak) when he mixes up his markets. Here's his advice for a mystery writer:
An example of a niche market is fly fishing enthusiasts. Let's assume that you've written a murder mystery that features a protagonist who is a master fly fisherman. You'd be well-served to pursue fly fishing blogs, magazines, websites, clubs, etc. Let them know about your book. Offer them review copies. Let them know you're available for an interview, personal appearance, or whatever else they need.
This is just wrong.
In my opinion, people who read fly fishing blogs like to keep busy fly fishing. Assuming they are interested in murder mysteries is going to appeal to a small fraction of those blogs' readership. They don't care about your book
A fly fishing club will likely spend their spare time getting for their next fishing trip, not a thrilling murder mystery read. They don't care about what you're busy writing.
Writers will have more success targeting this group with a non-fiction, how-to title.
Yes, there will be SOME hobbyists who will see the book and be intrigued enough to buy your new work of fiction. But they are not your best niche to chase after.
Again, SOME will buy your book. But at what cost? Better yet: A what return on investment of your time, effort, and advertising expense?
The good thing is that the Kindle e-book store and Createspace itself are incredibly effective at allowing an author to reach his or her niche. Readers seek out their own genres they want to buy. Targeted keywords and complete descriptions are the best way to reach these readers.
Not bothering them when they're busy with what they are really interested in.
Put your fiction in front of readers. Put your non-fiction in front of people with problems they want to solve.
You'll sell more books that way.
And spend less time chasing people who aren't wanting to read what you write anyway.