There are four books of knowledge to be found in Grantebridgescire, which provide the Mark of Death ability, Incendiary Powder Trap, Rush & Bash, and Dive of the Valkyries.
Mark of Death
This Book of Knowledge is located in a tower in the south of Meldeburne, which is a raiding location. To unlock the door to the tower, you’ll need to locate the enemy holding the key, which you can do by using Odin’s Sight.
Incendiary Powder Trap
This Book of Knowledge can be located in the Church in Walden, and the main quest Unholy Father will take you directly to the area. The Book of Knowledge is nearby the Priest who you’ll need to assassinate.
Rush & Bash
This Book of Knowledge is located in Ravensburg, which you will go to during the main quest, Storming Ravensburg. The book is located within a locked house, and to unlock the door to the locked house, you’ll need to locate the enemy holding the key, which you can do by using Odin’s Sight.
Dive of the Valkyries
This Book of Knowledge is located in The Isle of Ely Monastery, which is a raiding location near Wycham. The Book is located beneath the Monastery, and can be reached via a tunnel on the shores.