Herrick's end. (The Neath trilogy, book 1.)

You did nothing. You were nothing. And so, you shall remain here, until the end of your days. As nothing. Ollie's only friend disappeared a few days ago, and now, he's frantic to find her. But he doesn't have much to go on until a mysterious note arrives which reads: "Still looking for your friend? I know where she is." Unfortunately for Ollie, the trail leads to the last place he'd ever expect. Somewhere dark. Somewhere deep. The kind of place where magic spills like blood, vengeance is merciless, and escape seems all but impossible. Worse still, it soon becomes clear that someone--or something--was expecting him. Now, time is running out. If Ollie has any hope of ever seeing home again, he's going to have to summon every last scrap of courage, smarts, and tenacity he can find. And none of it will matter if he can't get some help. Fast. Because Ollie might not know much about the vast underworld that's ensnared him, but he does know this: He'll never make it out alone.