This book was initially hard to get into, since the author tried to use first person narrative in early medieval style/tone especially alluding to or addressing animals and inanimate objects (like rivers) by formal names. Once I got the hang of it the story became very dear to me.
The main theme is that true saints are not "saints" because they are better behaved, but they are saints because even in their sin they intentionally receive the grace and love of Jesus. Saints live the experience that "nothing can separate us from the love of God..." according to Romans 8: 38-39 (actually my grandmother's favorite verse!)
Subtle, gracious, splendid; read it!
For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come, nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.