Kindred is a very good book, but it's not the easiest book to read. At no point did I ever feel like this book was going to have a happy ending. It is, of course, a novel about slavery in the antebellum Southern US, so you might expect it to be bleak, and it isn't coy about describing the violence and terror that Black people endured – things like brutal lashings, having your children our spouse sold away from you, or even the fact that free Black people were expected to be able to prove their status at all times with a certificate, and if a slaver took it off them and ripped it up, that slaver could then abduct them and sell them on. It's so important for people to know about this history, and as such novels like this play an important role keeping that history alive in the public memory.
The novel is ostensibly science fiction, but only really in getting the main character to the setting where the story takes place – otherwise it's more historical fiction. The protagonist is Dana, an African-American woman living in 1976 Los Angeles, who keeps getting sucked back in time to save the life of her ancestor (a red-headed white boy at the story's start, later a man – and a slave owner). The time travel element is never explained, or even investigated; it's really just a plot device so the attitudes of those living with slavery can be contrasted with Dana's modern sensibilities. Dana has no real control over her coming and going, though, so despite those modern sensibilities she has to find a way of surviving in the 19th century as a slave. This is also the source of a lot of the story's disquietingness; Dana is faced with a number of choices where every possible option is utterly repugnant, and while you might hope she finds a way to short-circuit the dilemma and pull a magical good outcome out of nowhere, she doesn't. Like I said, it's not the kind of book where happy endings ever seem realistic.
The book does share some similarities with other books I've read by Octavia E. Butler. Like them, the prose here is sparing and utilitarian – rather than lush description, Butler's strength is more in the dialogue and character dynamics she brings forth. And Dana here is a very similar character to some other Butler protagonists, particularly Lilith in Dawn, in the sense that a reader can understand but still wish she'd make some different decisions (like here, you wish Dana'd be harder on her slave-owning ancestor, even though you understand why she can't!). These factors might deter some readers, and contribute to me rating this three stars, but it's still a very worthwhile book.