I tend to view spiritual books as the opportunity learn wisdom, beauty, and holiness at the feet of remarkable authors past and present. One such author is Jean Pierre de Caussade, S.J.
"Now that you are less busied with others, spend more time in nourishing your soul with good reading. To make this nourishment the more beneficial, let this be your method of taking it. [1.] Begin by entering the presence of God and by begging his help. [2.] Read softly and slowly, a word at a time, that you may interpret your subject with your soul rather than with your intelligence. [3.] At the end of each paragraph containing a finished thought, pause for as long as it would take you to say an Our Father, or for even a little longer, to appreciate what you have read or to rest yourself and to gain interior tranquility before God. Should this rest and tranquility last longer, so much the better; but when you notice that your attention is wandering, [4.] go back to your reading, constantly making similar pauses as you continue" (DE CAUSSADE, J.P., S.J. Self-Abandonment to Divine Providence. page 191).
It's not about how many books you read or even which ones you read. It's about how well you read. This is why I often say to our patrons, as I hand them their books from behind the checkout counter, "read well".