Soapbox time. You've been warned.
First, some relevant links:
VIDA: a look at statistics involving women authors, reviewers, and reviews. (Lots of graphics for the not-statistically-minded.)
Strange Horizons: a look at the same in the science fiction and fantasy genre.
Author Keri Sperring on "Why I Started #womentoread": in which a sff author asks for recommendations of female sff authors to give to people who may be missing them because of a lack of marketing promotion.
Now that you're up to date, I hope we can all agree that there is a discrepancy in that data, namely that women are under-represented in reviews relative to the number of books they publish. From my experience as a bookseller, there are two types of books: frontlist titles (i.e. those on display, usually easy to spot because you see the cover instead of the spine) and backlist titles (i.e. on the shelves). In a brick & mortar store, frontlist titles are the overwhelming majority of sales. A former manager of mine once quoted frontlist as 70% or more of the sales for the store; in the children's department I ran, that was definitely true (we were required to keep weekly sales logs, so I had the data to prove this). So, if your books are only in backlist, your sales will be commensurately lower. I know from 5 years' experience that simply putting a book or series on a display does increase its volume sold, regardless of price.
The internet and social media can be a powerful tool for equalizing the playing field between traditional marketing and deserving authors. Marketing is all about an information disadvantage: the marketers or retailers know what you've been buying, how much an item actually costs to produce, and whether you can get it elsewhere. They set their prices and displays to encourage you to think you need it right here, right now. The internet can let you know that you do have a choice. Your expenditures in retail are tracked and stores respond!
I don't have a twitter account, so here's my contribution to Sperring's #womentoread request. I have read and enjoyed every one of these authors immensely.
Mary Robinette Kowal: Alternate history fantasy novels set in Regency-era England; her portrayal of that society and the characters within it are really exquisite.
Anne Bishop: dark fantasy, particularly known for her powerful characters.
Kate Elliott: epic fantasy, fantastic characters, and a serious look at the societal forces that shape a person.
Robin Hobb: epic fantasy, complex characters who change realistically with events.
Kate Forsyth: Celtic fantasy, sword & sorcery, great page turners.
Jacqueline Carey: alternate history/mythology fantasy, set in Europe (mostly...). Great spy & intrigue novels.
Trudi Canavan: high fantasy, lots of magic, easy reading that really pulls you along.
Madeleine L'Engle: probably the first female sff author I ever read. Mostly children's/YA work, magic-within-our-world plots. A great entry point for younger readers.
Karen Traviss: I've only read her Star Wars work (although her own novels are on my to-read list) but, even by non-SW Expanded Universe standards, her books are excellent. She fabricated a whole culture and populated with realistic characters who react and grow into it.
C. S. Friedman: Epic, high, dark fantasy; mind stretching sci-fi. I cannot recommend her highly enough to fans of "traditional" sff.
These are just the ones I read and liked. There are so many others that may speak to you! Browse those bookshelves or use a dedicated reading site like Goodreads to find a recommendation!