Authors have two main questions when it comes to book reviews:
1) Where do you find the reviewers?
2) How do you get books to those reviewers once you find them?
Reviewers can come from anywhere. The well-known reviews from Kirkus, Publishers Weekly, and the like handle mainly traditional books. Often there are costs to achieving these reviews in terms of payment, membership, or subscription. Indies have an uphill battle as do the smaller of the small presses. And you already know that competition is fierce, so assuming you can get some of these bigger sites to accept your book, the wait might be for months.
Consider these reviewers:
1) The Indie View - http://www.theindieview.com/
2) Omnimystery - http://www.mysteriousreviews.com/mysterious-reviews.html
3) NPR Books - http://www.npr.org/books/
4) Net Galley - https://www.netgalley.com/
5) eBook Crossroads - http://www.ebookcrossroads.com/book-reviewers.html
6) RT - http://www.rtbookreviews.com/
7) Goodreads - http://www.goodreads.com
8) Midwest Book Reviewers - http://www.midwestbookreview.com
9) List of other reviewers on MBR - http://www.midwestbookreview.com/links/othr_rev.htm
10) Book Review - http://bookreview.com/$spindb.query.bottom.booknew
11) Publishers Weekly - http://www.publishersweekly.com/