read fewer books but read them with greater care
There are many valid reasons to read, but if you’re about self-improvement in one way or another — an increase in knowledge or insight or, hey, even wisdom — then one of the most reliable ways to become a better reader is to read fewer books but read them with greater care. If you would be wise, an essential book you know intimately — through slow reading or repeated reading — is of more use to you than a dozen lesser books that you know only casually.