That question just dredged up a massive, dusty chunk of my old reading history. I have a weirdly specific memory of late-2000s YA angel fiction, where the default setting seemed to be fallen angels wrestling with guilt and seeking a second chance. 'Hush, Hush' and 'Fallen' come to mind immediately—though honestly, looking back, those felt more like paranormal romance vehicles than deep theological explorations. The redemption arcs were sort of... surface-level angsty? Like, brooding over past mistakes while making out with a human girl.
If you want something that genuinely grapples with the weight of those concepts, I'd point you toward 'The Angel's Game' by Carlos Ruiz Zafón. It's not your typical heavenly warriors story; it's a gothic labyrinth where the idea of grace gets twisted into a Faustian bargain. The protagonist's pursuit of redemption is dark, messy, and ultimately questionable. For a more classic, haunting take, Susan Howatch's 'Starbridge' series, especially 'Glittering Images', uses an Anglican church setting to dissect spiritual crisis and grace in a way that feels painfully human. Those books left a deeper mark on me than any winged-warrior saga ever did.