Angels and demons aren't something I personally write about in my books  Not to say I never will  LOL I've learned to never say never when comes to writing something  But I do read book with them. Of the angel variety, I have to say one of my favorites is Clarie Delacroix (otherwise known as Deborah Cooke, to those familiar with her dragonshifter series)  angel series  The first of which is Fallen which is the one I reccommend the most.

They always seemed borderline steampunk to me, with a futuristic-like setting but Victorian-era clothing and such. Of course, this was before the steampunk genre had really taken off. Definitely worth checking out if you're looking for something new or  little different!