Estoy a un doce porcileyentdo a través del libro Reina roja por, de Juan Gómez-Jurado y voy por el doce porciento.

I think it's clearer when you say what you are doing first and then at which page or percentage you are.

Acabo de llegar al pumomento en que se explica que el título se refiere a un personaje de otro libro, Alicia en el país de las maravillas porde Lewis Carroll.

In Spanish, when you say "by an author", you say "de" because it's that author's book.

Es mi primera novela policíaca y tengo ganas de ver queé va a pasar.

"primera" is an adjective that needs to be the same gender as the noun.
"qué" instead of "que" because now it works as a pronoun. Whatever happens vs. that happens... (something)