For good-aligned characters, a copy of the book is located in the South Qeynos mage tower (red teleporter), down the stairs, on the floor between Aristide Calais and Rune Shimmerstar.
For evil-aligned characters, a copy of the book is located in the Academy of Arcane Science in North Freeport, a small black book standing on edge on one of the tables on the first floor. The North Freeport book is leaning against two other stacks of books behind the sage.( 12, -6, -134 ) /waypoint 12, -6, -134.
You can pick up the book in your friendly city no matter which faction you are working with.
Speak to Dirin Thilae again.
Right-click on the torch near Dirin Thilae and move it closer to him while he reads. The torch will despawn then respawn in the same spot in about two minutes, in case you are doing this in a group.
Spawn and kill Dryxl T'Rath by running over the red pentagram ( -89, -37, 90 ) /waypoint -89, -37, 90. Once killed, his spirit will appear and float towards the crypt entrance above the pit in which the pentagram appeared.