YA Sci-fi novel, time travel with steam punk elements and blimp. Read in 2010-2014.

[Alexander]

I wrote notes about this book 5 years ago that I'm attempting to decipher. General plot was there was a young protagonist that had to make an important decision, and this decision led to 2 alternate timelines occurring. I believe in one of them the antagonist returns with a blimp 70 years later. Despite the time travel, I remember there being a sort of steam punk theme throughout the book. Any help is much appreciated. Thank you

[Rainbowheart]

Was the main character male or female?

Teenager or younger child?

[Casey]

Could it be The Vengekeep Prophecies? I haven’t it read it in awhile but it has steampunk elements.

[Reader]

Leviathan
Scott Westerfeld

[Alan]

Leviathan and The Vengekeep Prophecies for the links.