12 Be warned, my son, of anything in addition to them. Of making many books there is no end, and much study wearies the body.

Read Ecclesiastes 12:12 Using Other Translations

And further, by these, my son, be admonished: of making many books there is no end; and much study is a weariness of the flesh.
My son, beware of anything beyond these. Of making many books there is no end, and much study is a weariness of the flesh.
But, my child, let me give you some further advice: Be careful, for writing books is endless, and much study wears you out.