I see a lot of people posting about authors I first found out about via following them on Twitter. For instance, Kameron Hurley, Adrian Tchaikovsky, Cat Valente. So let me tell you about an author I first found out about on Twitter: Foz Meadows.
Strictly speaking, I'm going to tell you about the first book of hers that I've read: An Accident of Stars. It's a portal fantasy, by which I mean it is a story that hinges around a portal to another world; think Narnia gate. It is not your typical portal fantasy, however, but modern, and much more gritty.
The hero is a young lady named Saffron, who in the opening chapters suffers from tolerated bullying and even groping in school ("Boys will be boys," says the principal) and is looking for help. Enter an odd woman on the school grounds, who talks to her to ask directions. Out of curiosity, she follows this woman, and finds her opening an odd region in space in a part of her school grounds.
The world she finds herself in is much more vicious and hard-core than Narnia; characters are mutilated, throats are cut, and a serious power struggle between two cultures makes up the exciting plot. I have, and will read, the sequel.
Among old-school authors, I have recently read Timothy Zahn's Thrawn. When Disney obtained Star Wars, they mostly dumped many of the follow-up plots and characters that had been part of the Star Wars Expanded Universe so that they could make the story their own. However, Zahn's memorable character Admiral Thrawn, from five (?) pre-Disney volumes, was chosen to survive into the new Star Wars universe, and this novel is his origin story.
Thrawn is a blue-skinned humanoid alien, extremely intelligent, and he is found by the Empire on a small backwater world where he was exiled by his civilization, which is unknown to the Empire or to the Republic. The story is told from the point of view of an unambitious cadet who only wants to have an undistinguished career and be left alone; Thrawn guides him up the ladder and past lots of perils. On the way, we see Thrawn as part Sherlock Holmes, part Sun Tzu, and all fascinating character.