Notebooks and codes

You may have noticed that a common theme throughout almost all of the Knave's sacrifices is that tha Marked carry a notebook, filled with His holy word. Indeed, if you yourself are Marked, and trying to escape the Sacrifice, you will probably find yourself writing one when the end draws near. Or maybe that's just me. Either way.

If my experiences are representative of the whole, you won't remember getting or writing in the Journal. It'll just appear, and whenever you slep, or lose time, it'll get a little more full. Codes and drawings and rambling and insanity, all in a neat little papery package.

My advice is to make sure you crack the codes in there as soon as possible, and note down the translations in the notebook. It'll save time if anyone investigates your metamorphosis. It shouldn't be too difficult; seems the proxies only use straight substitutions. Still, there is one code I've been having trouble with. If nobody minds helping out, it'd be much appreciated.

20/12/13/16///
29/19/25/22//24/13/17/9//11/4/22//7/19/17/9//28/30/27/27/14/23/13/14/27///
29/19/25/22//6/20/12/10/23//11/21//28/26/12/19/12/26/26///
29/19/25/22//28/15/29/19/29/30/11/24/13/15//11/21//12/27/26/15/18/11///
28/30/27/27/14/23/13/14/27//4/17/7//15/8/7//15/7//16/13/26/9//4/17/7//27/5/16/15//23/11/8//10/6/23/25/13//3/21//2//24/22/25/9//26/12/25/29/8/21/27//17/8//23/11/8//16/19/22/8///
28/18/24//8/28/28/12/20/23/27//22/17//12/11/26/26/11/24//15/7///
8/23/6/11/25//

Far as I can tell, it isn't a simple substitution.