Just in time for her 31st birthday on Sunday, Taylor Swift has gifted fans with yet another surprise album. And what a bounty it is. “Evermore,” out now, is the 10-time Grammy winner’s ninth studio album and second this year after “Folklore,” her retreat into fanciful fireside folk after three albums of boldfaced stadium pop.

Coming less than six months after “Folklore,” a songwriting masterclass that produced some of the best music of Swift’s already prolific career, “Evermore” continues the ethos of its predecessor: twinkling piano, lush strings and plucked guitar, as Swift spins vibrant yarns about real and imagined characters. And like her last album, this new one is cowritten and produced by The National’s Aaron Dessner and Bleachers’ Jack Antonoff.

But “Evermore” is no ragbag of “Folklore” B-sides and throwaways. Rather, it’s a sister album that only crystallizes Swift’s strengths as a songwriter, as she moves further away from the candid autobiography that’s defined her music since her 2006 debut. Much of its 17 tracks are “mirrored or intersecting” tales, Swift explains in the liner notes, dripping with murder and intrigue and tortured romance.