The concept is interesting.
But I'm a little confused by the variation in size of different video medias or images. which forces me to constantly have to close the left menu, to be able to access the icons leading to the rest of the story.
I think also the image of the magic book doesn't need to be so big either, to stay permanently displayed; a vertical bar of small icons for each unlocked spell would be very useful.
In short, consistency in the size of images and videos and a UI to be reviewed for greater comfort. small inconsistency in the story as well, the fact that we don't need mana for the first two spells cast in the library, then afterwards, we need mana to use this same spell.
I understand why you integrated mana, to force players to make choices, but in this case, it must be integrated from the first use of the very first spell.
I have not yet explored all the avenues, notably the aunt and the cousin, by having body-change with his cousin.