The Girl with the Windup Heart by Kady Cross

Genre:  YA Steampunk

The Steampunk Chronicles, Book 4

Kady Cross' website

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Note:  If you haven't read this series, the information below could spoil plots from earlier books.

Description (taken from Kady Cross' website):

1897 London, a final showdown is about to begin

London’s underworld is no place for a young woman, even one who is strong, smart and part-automaton like Mila. But when master criminal Jack Dandy inadvertently breaks her heart, she takes off, determined to find an independent life, one entirely her own. Her search takes her to the spangled shadows of the West End’s most dazzling circus.

Meanwhile, taken captive in the Aether, Griffin King is trapped in an inescapable prison, and at the mercy of his archenemy, The Machinist. If he breaks under the hellish torment, The Machinist will claim his powers and control of the Aether itself, and no one in either world will be safe—especially not Finley Jayne and her misfit band of friends.

Finley plunges headlong into the Aether the only way she knows how, by temporarily dying. But she cannot parry The Machinist’s maneuvers for long. To defeat him for good, Griffin will have to confront his greatest fear and finally come face-to-face with the destructive power he wields.

This is a steampunk series told from multiple points of view.  We have Finley/Griffin, Emily/Sam, Wildcat/Jasper, and Mila/Jack.  It seems like new characters are creeping in and everyone's got a partner to love.  Regardless, this story gets to introduce Mila a little bit more, and the story weaves through her relationship with Jack.  It looks like bad boy Jack might have finally found a reason to be happy.

Garibaldi, Griffin and the gang's arch nemesis, was finally destroyed in the last book.  But now he's in the Aether, and he's out to get Griffin.  So when he finally does capture him, all hell breaks loose with the gang as they try to figure out how to save him.  But Finley will stop at nothing to save the man she loves.  Even if it means destroying herself in the process.

Honestly, I have fun with this series.  I can't really say I remember exactly what happened in the previous books since it's been a year in between books, but I still enjoy reading them.  Sometimes, the multiple points of view get to me, but I think it went well with this one.  I got enough from each character to stay content but was left with a little mystery to want to keep reading.

This is an original steampunk series that keeps going.  If you haven't looked into it, I'd suggest you read the first one.  It might catch your eye (and keep your heart).