The book is in the Scarlet Monastery Library. It's hanging off of a bookshelf on a short wall in the last hallway before the final boss. This is a level 38 quest (I believe), so you might want to kill the final boss because has some pretty good mage drops for around that level, maybe a bit lower though.

Leads to this quest (rewards): https://vanillawowdb.com/?quest=1952 https://vanillawowdb.com/?quest=1952

you can solo this at lvl 44 if you are patient and careful. there are key points where you probably will not aggro anyone, even the wanderers. What I did was get 5 invisibility potions. Go to the entrance of the Library, you will see 2 npcs right at the doorway. hug the wall and scoot by. drink one pot, and run immediately down the hall and across the courtyard to the door. Immediately turn right, there is a safe spot you can wait for your pot cooldown to end (Alphamap coords approx 74,89). Drink your next potion and run down the hall to the door on the RIGHT. keep to your right and into a corner of the next hall (coords 77,80). Hug as best you can into the corner. drink the next potion, and run down the hall, turn RIGHT, then immediately go LEFT into the corner (coords 81,70). make sure to stay in the corner because there is a npc that walks by. Next pot, run down the hall again, the book is on the left, so go left into the corner. you should be able to get the book while standing int he corner, so you will not aggro the 2 NPCs standing there. then hearth home!