I have an 8yo DD who loves books. She has several on the go at once. Loves the library. As a sleepwalking toddler, she was often found in the dark, 'reading' a book by her bookcase.
She's dyslexic. Her reading level is low. Fir her to properly enjoy a book, she need someone to read it to her. We read loads together (currently Carries War, and Harry Potter) Alongside that, she has simpler stuff she reads herself. It's stuff like Rainbow Fairies, which is pretty awful. But, that simple, repetitive language means she can relax and read and get lost in the plot, rather than struggling to remember if 'look' has an a long or short 'oo' sound, so it makes sense in a sentence.
Her 7yo sister lives Adventure and Mystery stories. Thinks the Famous Five us great- it's old fashioned, but a group of kids going off having adventures fires her imagination. She reads loads of modern stuff too.