Symbolism, Imagery, Allegory
Manley's hollowed out Bible, filled with booze, cards, and condoms, seems like a no-brainer as a symbol. His hollowed out Bible represents the hollowness of his belief in Christianity—it just isn't there.
Perhaps he worships bo oze, cards, and condoms (or sex) instead. His belief in these things certainly isn't empty since he's taken the time to fashion the Bible into a little carrying case with which to covertly transport them. It's a very purposeful thing to do. And because Manley is so hard to in down—more on this over in the "Characters" section—this hollowed out Bible and its contents basically tells us all we know for sure about Manley: He's deceptive, he's indulgent, and he has decidedly non-good-Christian-young-man appetites.
In short, there's more to Manley than meets the eye… just like with his Bible.