The speaker treats everything as a book: rain, a hand, an ear, even a confessor. That repeated word blurs the line between reading and living. A "book of rain" held in "the book of my hand" suggests something fleeting and weather-like being gathered into a person's own body, and the poem keeps folding one kind of reading inside another.
The tone turns quieter and more tender as it goes. One thing is "so long / it is not fit to publish," which sounds like experience too large or too private to become a finished text. Listening to confession seems to be a kind of reading too, with the ear acting as a preface. Then comes the plain line "I am sorry for the book / I am reading now." The speaker's feeling is sympathy, even heaviness. The last lines point to what lies behind it: what people believe, and the grief that comes with those beliefs. The mood is hushed, reflective and a little sad.