Reading Christian books can certainly help create in us a real desire for MORE of God's fullness, and for a more spiritual life.
It's especially helpful in regards to prayer. When our spirit is low and we have no inspiration for prayer. Even the reading of a spiritual poem can stimulate the mind, raise the spirits and REFRESH the soul. It can make it easier to pray, as well.
As to what books to read, the BIBLE, of course, is the best of all.
However, we may need other books as well. Although no other book can take the place of reading the Bible, and none of us should ever neglect reading it, there are many Christian books that can be read in connection with it.
Whatever devotional book you're reading, don't read too fast. Think and digest it as you go.
Furthermore, let there be a frequent lifting of the heart to God in PRAYER. It's not the bee that flies so swiftly from flower to flower that gathers the honey, but the bee that goes down into the flower.
A few sentences taken into the mind and heart, and dwelt upon until they've become a part of you, are better than many pages read superficially.
However, nothing beats reading the BIBLE.
"For the word of God is quick, and powerful, and sharper than any two edged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart." - Hebrews 4:12.