The British Library is on the cusp of increasing the collection of it's iPad app to 65,000 works, the app already contains around 40,000 fully digitised copies of novels, ancient poems, and historical accounts.
While it does cost (£1.99 a month), the increase of around 25,000 is just the next step in making as much of their collection available on the move. If that wasn't enough it's also in partnership with Google to digitise a further staggering 250,000 public domain works.
The works have been painstakingly digitised and are available with all the original drawings and annotations, because of the way they have been digitised however the files are of an extremely large size. What this simply means is that the whole collection remains in the 'cloud' ready to be accessed via the app.