The Flash: Supergirl's Sacrifice (Crossover Crisis #2) by Barry Lyga

Those with super powers are working on saving the world but it's not easy.  They've already lost a couple.

Abrams shared this book with me for review (thank you).  It has been published and you can grab a copy now.

Cisco and Curtis are still lost in time.  They don't know whether they went forward or back but finding a pile of bison heads gives them a clue.

They are still harboring a few thousand speedster refugees, there is a mad bomber in town, and the Anti-Matter man has just shown up. 

With the forces all working to stop tragedy, there aren't many left to fight new dangers.  Supergirl takes on the Anti-Matter man and stops him, but he's stopped her, too.  She saved Superman earlier in the story, can he save her now?

There's lots of action, lots of plot, and plenty of excitement.  And it's not over yet!