Here are some social media platforms that can help you promote your book for free. Although they allow promotion, most of these platforms are not strictly promotional. Their main purpose is to host discussion groups, book clubs, and writing critique groups.
In addition to the ever-present necessity of promoting your work, I would encourage you to take advantage of these non-promotional functions for two reasons: 1) As a writer, it's essential to participate in discussions about your craft and genre, and 2) You may make some valuable contacts with other authors in the course of those discussions. (I did.)
Facebook is a huge social media platform, which means it can produce dramatic results. First, set up a page for your book. (This is a must.) Then join writers' groups. The largest and most active writers' groups are listed here: 43 Facebook Groups for Authors. There are also several active Facebook groups geared specifically to science fiction and fantasy writers. These are:
Fantasy & Science Fiction Writers in America. (Closed group) This is for writers who focus their work mainly on science fiction and fantasy. The site is for writers to post small pieces of their work to get others' opinions on them, to offer or request advice about the art, craft, and business of writing, and to exchange interests concerning science fiction and fantasy writing with like-minded individuals.
Cyberpunk Science Fiction & Culture (Closed group) Group dedicated to all things related to cyberpunk: culture, literature, music, film, technology, games, fashion, lifestyle, etc.
Science Fiction and Fantasy Authors. This group is open for anyone who loves the genres of science fiction and fantasy. They welcome readers, writers, viewers and all lovers of the genres.
Science Fiction. (Closed group) For all those interested in science fiction and fantasy adventure reading.
Space Opera. Space opera is a sub-genre of science fiction dealing with stories of epic adventure and conflict on a grand scale. If you are a fan of authors like Poul Anderson, Peter F. Hamilton, Alastair Reynolds, E.E. Smith, David Drake, Neal Asher, John C. Wright, Iain M. Banks, Walter Jon Williams, Dan Simmons, Jack Vance, David Weber, Vernor Vinge, Stephen Baxter, Larry Niven, or Louis McMaster Bujold, this group is for you. Authors can promote their books through special promotion threads.
Science Fiction and Fantasy Books Fans. This is a virtual book club of fans of science fiction and fantasy.
SciFi,Horror,Endoftheworld,Truestory.,other,Books,Screen,Music,Writers. This group is for authors, novelists, screenwriters, and bloggers to share their pages and/or published work.
We PROMOTE Fantasy/Sci-Fi Writers/Authors - "If you need help promoting your work, my Sci-Fi/Fantasy Team can advertise your book in our active Facebook fantasy & sci-fi page with 117,000+ Likes, Twitter page with 20,000 Followers, and feature it in Fantascize.com. We can also help you reach thousands of readers through book reviews, author interviews, book trailers, and any other type of advertisment/promotion you may need. For more details, Email my team at firstname.lastname@example.org or me personally at email@example.com if you're interested."
SciFi and Fantasy Book Club (15669 members) - This is mainly a discussion group, but there is also a folder for authors to promote their books. Make sure to read the rules before posting.
SciFi and Fantasy eBook Club (3538 members) - Self-promotion is allowed in the Authors' forum for active members.
Dystopia Land (2047 members) provides a folder where authors can post releases, giveaways, free books, and short stories.
#PNR (Paranormal Romance)
#ScifiRTG or #SFRTG (Sci-fi Retweet Group)
#IFNRTG (Indie Fantasy Re-tweet Group)
#IARTG (Indie Author Re-tweet Group)
#YA (Young Adult)
#BYNR (Be your next read)
Google + communities are an ideal platform for book promotion. These communities are lively, and posting is effortless. (All you need to do is post a URL and a brief intro.) Before you start joining Google+ communities make sure you have set up an attractive profile on Google. It's easy to do, and I guarantee people will be visiting. (My profile has gotten over 5 million views.) You can also set up a page for your book. Don't forget to read the rules of the groups before posting!
Speculative Fiction Writers - This Community is a place where all writers of science fiction and fantasy, from brand new to published authors, can come together to share trials and triumphs in developing new worlds, human and nonhuman characters, and stories large and small. (No promos)
Science Fiction Writers - Any and all discussion related to science, fiction, or any intersection of the two is welcome. This community does not allow self-promotion, but feel free to post book reviews and announce the release of your latest work.
Science Fiction - Authors, please feel free to post information and links for your books, blogs or other promotions, but please be sure to do it into the correct category and be sure to limit your self-promotional posts to once per week.
Fantasy Writers - All active members who post and comment on writing-related topics are welcome to promo their work on Saturdays.
Reddit is underutilized for promotional purposes, probably because the site actively discourages self-promotion and ads. Nevertheless, several authors have been "discovered" on Reddit, and have developed sizable fan bases, usually through r/books and its subreddits. (The trick to Reddit is knowing which sub-reddit is appropriate for your topic.)
r/books. This is a very active community dedicated to the world of books. There are no direct promotions allowed on this page, but they do have a “new releases” section where you can promote your book. You are allowed to promote your own writing in "new releases" as long as you follow these two rules:
- The books being discussed must have been published within the last three months OR are being published this month.
- No direct sales links.
All the sci-fi related subreddits have been collated into a Big list of SF-Related Subreddits. There are too many subreddits to list here, but if you take a quick look at the Big List you will find many in the "writing" section that will be useful. (Also make sure to check the genres list.) There are two sub-reddits that are particularly active, and which allow some self-promotion. (Please read the rules before promoting your work!)
r/scifi (238,420 readers) Saturdays “self-promo Saturdays,” so log in on Saturday to promote your book. If you look at the side bar you'll find numerous subreddits, and within those even more sub-subreddits.
r/sciencefiction (34,189 readers) This reddit is for fans and creators of science fiction and related media in any form.
Pinterest is a great tool for sharing information. You can set up a board for your own publications and include photos of your book covers, signing events, and anything else related to your writing. You can also set up a group board devoted to related science fiction or fantasy topics, such as self-published science fiction or your favorite classic science fiction books, and allow others to share their titles. You can join established boards as well. (This is a great way to get followers.) Here are some group science fiction and fantasy boards that welcome new pinners:
SciFi Books – Community Board
Sci-Fi & Fantasy Books
Indie Authors and Self Published
! Sci-Fi & Fantasy Books
For more detailed information about how you can make best use of Pinterest see: How to Use Pinterest to Build an Audience (For Writers)