Library of Leng

If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Null Profusion (an enchantment that says your maximum hand size is two) onto the battlefield and then put Library of Leng onto the battlefield, you'll have no maximum hand size. However, if those permanents entered in the opposite order, your maximum hand size would be two.

Since the card goes directly to the library, the card is not revealed unless the spell or ability requiring the discard specifically says it is.

This effect has no effect on the cards being put into the graveyard from a library, because they are not "discarded".