"I read book in my room" doesn't make sense in English.
You are however at liberty to say "I read a book/books in my room." These sentences are the same in English. The only way you can disambiguate is you you put "bir" in front of kitap to make it clearly mean "a book" :)
I would place a time clause in front of the locative, as the "natural" word order. For example "Her gece odamda kitap okurum." - "Every night I read a book in my room". This word order could be changed, though, if you want to emphasize the "every night" aspect: Odamda her gece kitap okurum.
That would not be grammatically correct. You cannot use the plural on a general direct object.
"Odamda kitap okurum." Translation: I read books in my room.
What would it be if the sentence were: I read books in his/her room?
I read books in his/her room. "Onun odasında kitap okurum."
I have used "kitap" in singular form.
To explain why?
The indefinite, direct object in the nominative case always goes immediately before the verb. Duo accepts both singular & plural forms.
I read the books in his/her room. "Onun odasında kitapları okurum."
"The books", the definite direct object with plural -lar suffix & accusative case suffix -ı.