A diary of about 700 printed pages!

The handwritten pages of Kowalska's diary turned into about 700 printed pages which were published as the book Diary: Divine Mercy in My Soul. The book reflects her thoughts, prayers and her reported visions and conversations with Jesus on Divine Mercy. Kowalska's Vatican biography quotes some of her reported conversations with Jesus from her diary.

It records the last four years of her life. It reveals the depths of her spiritual life and illustrates the high degree of her soul’s union with God. The Lord endowed Sister Faustina with tremendous graces: the gift of contemplation, a deep knowledge of the mystery of the mercy of God, visions, revelations, the hidden stigmata, the gifts of prophecy and of reading human souls, and also the rare gift of mystical espousal.