The figure of Hudibras is a "true blew Englishman," a perfect Puritain knight of the Cromwellian stamp (see the entry on Oliver Cromwell for more). Butler pretends to write a fawning, heroic poem in praise of Hudibras and his exploits, but the poem is a mock heroic or parody.
"Hudibras" was written in an iambic tetrameter in closed couplets, with surprising feminine rhymes. This verse form is now referred to as "Hudibrastic." Consider the following from the opening of the poem, where the English Civil War is described thus:
"When civil dudgeon first grew high,
And men fell out they knew not why?
When hard words, jealousies, and fears,
Set folks together by the ears,
And made them fight, like mad or drunk,
For Dame Religion, as for punk;
Whose honesty they all durst swear for,
Though not a man of them knew wherefore...."
For a text of Hudibras on the web, see 
The second Samuel Butler was born on December 4, 1835, in Langar Rectory, near Bingham, Nottinghamshire, England. As a young man he moved to the then new colony of New Zealand, and wrote a description of his life there entitled A First Year in Canterbury Setttlement. On his return to England from New Zealand, his satirical novel Erewhon was published anonymously, causing some speculation as to the identity of the author; when Butler was revealed as the author, there was some disappointment that it was not any of the more famous personages speculated about.
Erewhon made Butler a well-known figure, and he wrote a number of other books, including a not so successful sequel, Erewhon Revisited. His semi-autobiographical novel The Way of All Flesh was not published until after his death, as he considered its tone of attack on Victorian hypocrisy would be too contentious.
Erewhon revealed Butler's long interest in Darwin's theories of biological evolution, though Butler spent a great deal of time criticising Darwin, not least because he believed that Charles had not sufficiently acknowledged his grandfather Erasmus Darwin's contibution to the origins of the theory.
He developed a theory that the Odyssey was written by a young Sicilian woman, and that the scenes of the poem were based on the coast of Sicily and its nearby islands. He described the evidence for this theory in his The Authoress of the Odyssey (1897) and in the introduction and footnotes to his translation of the Odyssey. Butler also translated the Iliad.
Links: A first year, Erewhon, Erewhon Revisited, The Way of All Flesh and several other of his works are available for free download from Project Gutenberg at www.gutenberg.net.
A biography by his friend Henry Festing Jones is also available from Project Gutenberg: 
The Authoress of the Odyssey is apparently out of print and not online; however, Butler's translations of the Odyssey and Iliad are available from Project Gutenberg.