I do picture people in my head, so I can see where you coming from, but I have issues with names, so many characters become a blur.
Audiobooks might be good, many of the better voice actors change tones and accents with the characters so it makes it easier tell them apart.
The other could just be write notes/draw pictures. When a characters description is first mentioned write down what they look like to keep that as a reference. You could then either draw them if your any good, or just type that description into google or an art AI and save that picture with the characters name. Anytime you think of it look down on your notes pictures.
I do picture people in my head, so I can see where you coming from, but I have issues with names, so many characters become a blur.
Audiobooks might be good, many of the better voice actors change tones and accents with the characters so it makes it easier tell them apart.
The other could just be write notes/draw pictures. When a characters description is first mentioned write down what they look like to keep that as a reference. You could then either draw them if your any good, or just type that description into google or an art AI and save that picture with the characters name. Anytime you think of it look down on your notes pictures.