Genshin Impact: Guide to Collecting Magic Books
This achievement requires placing all the magic books back into the eight mysterious bookshelves in the Fading Castle, as shown in the picture. The 5th, 6th, 7th, and 8th bookshelves are located in the same corridor, and you can see all the bookshelves by following the path.

The first bookshelf is located on the lower level of the Fading Castle; proceed forward from the teleport point and you will see it on the left side of the path.
The second bookshelf is also on the lower level of the Fading Castle; after ascending the stairs, turn left and you will see the second bookshelf at the corner of the stairs.
The third bookshelf is on the upper level of the Fading Castle; after ascending the stairs, turn right and then right again, and follow the appearing stairs up to the top to find the third bookshelf.
The fourth bookshelf is on the lower level of the Fading Castle; turn right at the end of the corridor and descend the stairs to find it, below the stairs leading to the third bookshelf.
The fifth, sixth, and seventh bookshelves are located in a corridor; you can find them by ascending the corridor clockwise.
The eighth bookshelf is at the top of the corridor; first, activate the mechanism opposite the seventh bookshelf to create a platform. Stand on the platform, which will take the character to the top.
Then, activate the mechanism in the bookshelf at the top, creating a teleporter that will transport the character to the eighth bookshelf.
Completing the activation of all eight mysterious bookshelves in the Fading Castle will unlock the achievement “For the Love of Books.”