As noted earlier, effective use of the Library requires reduced hand size. One way to do this is to rely on your opponents; another is to play +Actions cards that don’t replenish your hand.
The third way is using the Vault’s ability to discard your cards for money. Play your +Actions cards, Vault your hand, then draw back up to 7 with the Library. Repeat as necessary. It’s a nifty strategy that can result in obscene amounts of money, though it does require quite a bit of +Actions to work effectively. It’s best in untrimmed decks with Coppers and Estates; in a Chapel deck, your average card is likely to be so valuable it’ll make little sense to feed it to the Vault for just $1.
Naturally, Watchtower can be substituted for the Library, and Secret Chamber can be substituted for the Vault. Additional Buys will likely be necessary as well, meaning Festivals and Worker’s Villages are probably the best sources for the +Actions for this combo.
This game also illustrates the Vault / Secret Chamber’s ability to get to Grand Markets very easily.
This game shows how this combo is also a great defense against Pirate Ship.