Some of the ulema would say that one of the reasons a person gets far in knowledge and one of the secrets is because when he studies something and goes through it again a second time or more, he still has the same honour for it as the first time he studied it. What usually happens is the second or third time he gets tired or becomes impatient.
Some teachers have read big 500 page books and thicker more than 3 or 4 times and sometimes 6 times.
Don’t think because you’ve gone through a book once you’ve done it and that’s it. You need to review, revise and go through it again possibly.
That’s why Jibreel would descend every year to go through the Qur’an with the Prophet (saw) in Ramadan!