According to Nassim Taleb:
A good book gets better at the second reading. A great book at the third. Any book not worth rereading isn't worth reading.
Seneca, the Stoic Roman philosopher, had something to say on this:
Be careful, however, that there is no element of discursiveness and desultoriness about this reading you refer to, this reading of many different authors and books of every description. You should be extending your stay among writers whose genius is unquestionable, deriving constant nourishment from them if yoou wish to gain anything from your reading that will find a lasting place in your mind. To be everywhere is to be nowhere. People who spend their whole life travelling abroad end up having plenty of places where they can find hospitality but no real friendships. The same must needs be the case with people who never set about acquiring an intimate acquaintanceship with any one great writer, but skip from one to another, paying flying visits to them all Food that is vomited up as sooon as it is eaten is not assimilated into the body and does not do one any good; nothing hinders a cure so much as frequent changes of treatment; a wound will not heal over if it is being made the subject of experiments with different ointments; a plant which is frequently moved never grows strong. Nothing is so useful that is can be of any service in the mere passing. A multitute of books only gets in one's way. So if you are unable to read all the books in your possession, you have enough when you have all the books you are able to read. And if you say, "But I feel like opening different books at different times", my answer will be this: tasting one dish after another is the sign of a fussy stomach, and where the foods are dissimilar and diverse in range they lead to contamination of the system, not nutrition.So always read well-tried authors, and if at any moment you find yourself wanting a change from a particular author, go back to ones you have read before.
Each day, too, acquire something which will help you to face poverty, or death, and other ills as well. After running over a lot of different thoughts, pick out one to be digested thoroughly that day. This is what I do myself; out of the many bits I have been reading I lay hold of one. My thought for today is something which I found in Epicurus (yes, I actually make a practice of going over to the enemy's camp - by way of reconnaissance, not as a deserter!)...
(Letter II in Letters from a Stoic (Robin Campbell translation)