Effective reading refers to critical reading which is important in academic writing. This kind of reading is not just to gain factual information. The purpose of this kind of reading is always to interpret and analyze. You are never to just take an academic passage as given but are to dissect it and draw out and analyze the ideas and evaluate whether they are valid or sound.
This kind of critical reading requires critical thinking which necessitates being able to logically take apart of ideas and their arguments and consider whether they make sense. An argument will be logically valid if its premises lead to its conclusion and sound if the premises are true.
Effective reading is important in an academic setting and is what students are supposed to learn in English class and be able to apply and practice in other subjects whether it be science, history, mathematics, or some other discipline.