Aziraphale is an angel in the novel Good Omens by Terry Pratchett and Neil Gaiman. The book summarizes him thusly: "Many people, meeting Aziraphale for the first time, formed three impressions: that he was English, that he was intelligent, and that he was gayer than a tree full of monkeys on nitrous oxide."
Pratchett said of the name, "It was made up, but from real ingredients." Aziraphale's name is an anglicisation of Aziraphael, and from the Hebrew elements we can glean that his name means "God heals my Strength."
On the pronunciation, he said, "It should be Azz-ear-raf-AE-el, but we got into the habit of pronouncing it Azz-ear-raf-ail, so I guess that's the right way now."
Unlike his counterpart Anthony Crowley, Aziraphale is given very little physical description. His hand is referred to as "plump," and Gaiman's unproduced screenplay refers to his eyes as "pale". Madam Tracy found him to be older than she had thought.
Aziraphale's fashion sense is a subject of teasing from Crowley. A section of the narrative told from Crowley's point of view remarks that "on those occasions when the angel managed to get his mind into the twentieth century, it always gravitated to 1950." Aziraphale is particularly fond of tartan.
In the Book
Aziraphale is the angel of the flaming sword who guarded the Garden of Eden before Adam and Eve were cast out (Genesis 3:24). In the opening of the book, he has just given the sword to the humans (reference to Prometheus of the greek mythology), citing the cold and Eve's pregnancy. The angel of the flaming sword in Christian theology is a Cherub, but it is later stated that Aziraphale is a Principality; his apparent loss of the sword may have contributed to his demotion.
He went on to become an agent of Heaven on Earth, under the guise of running a second-hand bookshop in Soho which is more a place to store his collection than a shop. Aziraphale does everything he can to discourage possible customers: he doesn't mark prices on the books, arranges them according to his own obscure system, keeps irregular opening hours, contrived strange smells and uses everything short of actual violence that can keep a customer from buying a book.
He collects prophecies, especially apocalyptic ones, although he's aware of the steps that have been taken to ensure none of them are accurate. Misprinted Bible editions are also a passion of his (he has a complete collection), as are Oscar Wilde first editions. When the last copy of The Nice and Accurate Prophecies of Agnes Nutter - the only book of prophecy that is never wrong - turns up, he is able to decipher them within two days.
Although God never directly appears, Aziraphale gets in touch with the Metatron (the Voice of God) for guidance in the event of the rapidly approaching Apocalypse. When directed to allow the war to proceed, he balks, and ends up joining Crowley and assorted humans to attempt to subvert the end of the world.
It becomes clear in the end that the Metatron is not as thoroughly informed about God's ineffable plan as one would expect.
Relationship with Crowley
Aziraphale has a strong friendship with his opposite number, the demon Anthony Crowley, who was the original Serpent of Eden. The two often meet up to compare notes, much like Cold War agents who find they have "more in common with their immediate opponents than their distant superiors."
Somewhere around year 1000 the two came to an Arrangement (the capital A comes from its "simply being in existence for so long"), according to which they would occasionally work together or do some of each other's work, because "it'd get done anyway, and being sensible about it gave everyone more free time and cut down on expenses."
In addition, during the course of the book they spend time together: they eat dinner at the Ritz Hotel, and, along with spies of all nations, regularly feed the ducks in St James's Park.
Crowley twice refers to Aziraphale as "angel."
Aziraphale's interests include "fascinating little restaurants where they know you," crosswords, antique shops, books, Regency silver snuffboxes and sushi.
He is "the first angel ever to own a computer", which he uses to do his accounts; these are so scrupulously accurate that the Tax Office have investigated him five times, convinced that he must be getting away with murder somewhere.
Although no sequel to Good Omens has been written, there is some information about Aziraphale's life beyond the book. The HarperCollins website features a list of his New Year's resolutions.