It's good for you, according to an article in the American Journal of Physiology — Heart and Circulatory Physiology.
The study investigated "the synchronization between low-frequency breathing patterns and respiratory sinus arrhythmia (RSA) of heart rate during guided recitation of poetry, i.e., recitation of hexameter verse from ancient Greek literature performed in a therapeutic setting," concluding, "recitation of hexameter verse exerts a strong influence on RSA by a prominent low-frequency component in the breathing pattern, generating a strong cardiorespiratory synchronization." (Via Ed.)
See, I'm not crazy — there's something to it when I talk about how a book "breathes." Science says so.