Here is the summary of the fourth book in the Hush, Hush series by Becca Fitzpatrick, titled "Finale":
Nora is more certain than ever that she is in love with Patch. Fallen angel or no, he is the one for her. Her heritage and destiny may mean that they will always be enemies, but there is no turning her back on him. But now they face their biggest challenge. Can their love survive a seemingly insurmountable divide. And in the end, will there be enough trust left to rebuild what has been broken? The lines are drawn - but which sides are they on?
So far no cover has been released.