You have been reading too many books. > "Have been" indicates an action taking place in the past lasting untill now ( present pecfect continous tense) > You were doing it in the past ( not specified in your sentence since when ) and you are still doing it.
You were reading too many books. > Sometime in the past , you were doing this but not now since you stopped that in the past too.) >Past tense
You read too many books.> This is what you do now >Present tense
You have read too many books. > You read a lot of book in the past until now .> Present perfect tense) , whether you will do it in the future is not certain.
Too many books > has a neagative conontation , meaning " overdoing" your reading of books.