Bonta imagines what happens when you truly give yourself to someone else's words. Reading, he suggests, means leaving your own "fixed residence," the familiar self you usually live in, which he calls "part coffin, part cocoon." It can be a place of deadness or a place where change is waiting to happen. Once you step out, the walls fall away, and the printed letters come alive with sirens and the call of a whip-poor-will, so the page becomes loud, wild and nocturnal.
The speaker sounds delighted and a little playful. "Anything can happen except sleep" makes the open book feel thrilling and wakeful. The joke about dreams being "redeemed / for a small deposit" nods to how libraries lend things out, as if imagination were another item you could borrow. The last line turns the idea around: everyone in a library is "homeless," because each reader has left their own house of self behind. The mood is light, but it carries a real sense of freedom, and perhaps a touch of vulnerability.