"You are reading a book in Spanish."
Translation:Tú lees un libro en español.
For "you are reading," you can say "estas leyendo" or "lees." In Spanish, you can use the present tense (lees) to mean the present progressive tense, so "lees" can mean "you read" or "you are reading."
The answer should be correct for both the "tú" and "usted" forms, since "you" was not specified as formal or informal.
I wrote "lees un libro en español" and my answer was accepted, but with the following correction: "Pay attention to the accents. Leés un libro en español." There should be no correction.
As you say, your answer needs no correction.
(vos) leés un libro is used in Argentina (I'm not sure if it's the whole country) and some other parts of South America.
The translation sounds more like "You read a book in Spanish" Estas leyendo sounds more natural for "You are reading"
"Usted está leyendo un libro en español" was marked wrong.
I'm surprised it was. I just answered that same thing and it was accepted. I'm guessing it's because you wrote "estas" (which is femenine for "these") instead of "estás" (you are).
It wouldn't mark it wrong for that. You may have put another mistake you missed.
It should be accepted (with a couple of typos: it's está and español).
Estas leyendo un libro en español . Was not accepted however the professor at the university says it is correct and the proper way to say it.