For Pride and Prejudice you don't need an extra text as you have to compare it with Letters To Alice by Fay Weldon.
For Henry IV I recommend you use the poem 'I, Too, Sing America' by Langston Hughes as it follows the theme of politics and people
For Discovery in particular Life of Pi I recommend you have a look into Invictus by W.E Henley as it shows the importance of spiritual discovery.
Hope that helps!