WoWDB

IMPORTANT:  YOU MUST HAVE AT LEAST ARTIFACT KNOWLEDGE LEVEL 4!

Additional notes:  There is a hidden weekly reset on this; and it appears that some books may have a respawn timer and spawn in a slightly different but nearby location from what is listed below.

This item unlocks a hidden skin called Tomekeeper's Spire for the Discipline Priest artifact,  Light's Wrath.  The process of obtaining it is not especially difficult, but will require time.  There are 12 volumes to collect which are spread out across Azeroth.  Buddy up with an Outlaw Rogue and take advantage of their  Find Treasure if you think you'll have difficulty spotting the books.

Turn all 12 in to Archivist Inkforge to receive Writings of the End.

Class Order Hall (Netherlight Temple)

• The Annals of Light and Shadow - Volume II is laying on a table behind Juvess the Duskwhisperer.
• Volume IV is on the bottom shelf of the bookshelf that is to the left of Meridelle Lightspark.
• The Annals of Light and Shadow - Volume VI is obtained from speaking with Archivist Inkforge.  Always choose the middle dialogue option.

Eastern Kingdoms

• Scarlet Halls dungeon in Scarlet Monastery, Tirisfal Glades  --  Found in the same room as the final boss, Flameweaver Koegler.  Kill him - may as well get the vendor gold - and then look on the left side of the room.  There is a table with a 3-pronged candelabra and a bench between the table and the bookshelf. The Annals of Light and Shadow - Volume VII is resting upon the bench.
• Scholomance dungeon in Scholomance, Western Plaguelands  --  Found in same room as the first boss, Instructor Chillheart.  Ignore the boss, you only need to kill the trash pack on the right. The Annals of Light and Shadow - Volume V is on the sixth bookshelf from the right.
• Karazhan raid dungeon in Karazhan, Deadwind Pass  --  (Shortcut:  There is a portal to Karazhan in the center of new Dalaran.)  Kill your way up to and including The Curator.  Jump down and to the right when you enter the Guardian's Library.  There is a tapestry with three bookshelves below it. The Annals of Light and Shadow - Volume XI is on the leftmost bookshelf, on the bottom shelf.

Northrend

• New Hearthglen, Dragonblight  --  (Shortcut:  There is a portal to Wyrmrest Temple in the center of new Dalaran.)  Entrance to New Hearthglen's church is at coords 72,73.  Enter the church and go left to the library wing.  The Annals of Light and Shadow - Volume III is on a bookshelf there.

Broken Isles

• Violet Citadel in Dalaran --  Behind Archivist Elysiana are two bookshelves.  The Annals of Light and Shadow - Volume I is in the bookshelf to the right.
• Black Rook Hold dungeon in Black Rook Hold, Val'sharah  --  Kill the first boss, Amalgam of Souls.  Proceed to the Map Room.  The Annals of Light and Shadow - Volume X is on one of the tables on the left side of the room.
• Azsuna  --  Dropped by vignette rare mob, Chief Bitterbrine.  Coords: 65.1, 56.5.  The gilgoblin is underwater in the captain's room of the shipwrecked Forsaken ship, the Queen's Reprisal.  The closest flight point is Shackle's Den.
• Stormheim  --  Dropped by vignette rare mob, Inquisitor Ernstenbok.  Coords: 63.4, 74.8.  The demon is in a cave (visible on zone map) near the shoreline southwest of Halls of Valor.
• Suramar  --  Dropped by vignette rare mob, Artificer Lothaire.  Coords: 33.8, 15.1.  The nightfallen elf is in the Moon Guard Stronghold, on what looks like an island (but it is connected by a rise of stairs) on the zone map.