Bunyan wrote The Pilgrim's Progress in two parts, the first of which was published in London in 1678 and the second in 1684. He began the work in his first period of imprisonment, and probably finished it during the second. The earliest edition in which the two parts combined in one volume came in 1728. A third part falsely attributed to Bunyan appeared in 1693, and was reprinted as late as 1852. Its full title is The Pilgrim's Progress from This World to That Which Is to Come.
The Pilgrim's Progress is arguably one of the most widely known allegories ever written, and has been extensively translated. Protestant missionaries commonly translated it as the first thing after the Bible.
Two other successful works of Bunyan's are less well-known: The Life and Death of Mr. Badman (1680), an imaginary biography, and The Holy War (1682), an allegory. A third book which reveals Bunyan's inner life and his preparation for his appointed work is Grace Abounding to the Chief of Sinners (1666). It is a classic example of a spiritual autobiography, and thus is focused on his own spiritual journey; his motive in writing it was plainly to exalt the Christian concept of grace and to comfort those passing through experiences like his own.
The above works have appeared in numerous editions. There are several noteworthy collections of editions of The Pilgrim's Progress, e.g., in the British Museum and in the New York Public Library, collected by the late James Lenox.
Bunyan became a popular preacher as well as a prolific author, though most of his works consist of expanded sermons. Though a Baptist preacher, in theology he was a Puritan. The portrait his friend Robert White drew, which has often been reproduced, shows the attractiveness of his true character. He was tall, had reddish hair, prominent nose, a rather large mouth, and sparkling eyes.
He was no scholar, except of the English Bible, but he knew scripture thoroughly. He was also influenced by Martin Luther's Commentary on the Epistle to the Galatians, in the translation of 1575.
Some time before his final release from prison Bunyan became involved in a controversy with Kiffin, Danvers, Deune, Paul, and others. In 1673 he published his Differences in Judgement about Water-Baptism no Bar to Communion, in which he took the ground that "the Church of Christ hath not warrant to keep out of the communion the Christian that is discovered to be a visible saint of the word, the Christian that walketh according to his own light with God." While he owned "water baptism to be God's ordinance," he refused to make "an idol of it," as he thought those did who made the lack of it a ground for disfellowshipping those recognised as genuine Christians.
Kiffin and Paul published a response in Serious Reflections (London, 1673), in which they argued in favour of the restriction of the Lord's Supper to baptised believers, and received the approval of Henry Danvers in his Treatise of Baptism (London, 1673 or 1674). The controversy resulted in the Particular (Calvinistic) Baptists leaving the question of communion with the unbaptised open. Bunyan's church admitted paedobaptists to fellowship and finally became paedobaptist (Congregationalist).
At one time, The Pilgrim's Progress was considered the most widely read and translated book in the English language apart from the Bible. The charm of the work, which gives it wide appeal among old and young, learned and ignorant, readers of all possible schools of thought and theology, lies in the interest of a story in which the intense imagination of the writer makes characters, incidents, and scenes alike live in the imagination of his readers as things actually known and remembered by themselves, in its touches of tenderness and quaint humour, its bursts of heart-moving eloquence, and its pure, nervous, idiomatic English. Macaulay has said, "Every reader knows the straight and narrow path as well as he knows a road on which he has been backwards and forwards a hundred times," and he adds that "In England during the latter half of the seventeenth century there were only two minds which possessed the imaginative faculty in a very eminent degree. One of these minds produced the Paradise Lost, the other The Pilgrim's Progress."
The images Bunyan uses in Pilgrim's Progress are but reflections of images from his own world; the strait gate is a version of the wicket gate at Elstow church, the Slough of Despond is a reflection of Squitch Fen, a wet and mossy area near his cottage in Harrowden, the Delectable Mountains are an image of the Chiltern Hills surrounding Bedfordshire. Even his characters, like the Evangelist as influenced by John Gifford, are reflections of real people. This pilgrimage was not only real for Bunyan as he lived it, but his portrait evoked this reality for his readers. Rudyard Kipling once referred to Bunyan as “the father of the novel, salvation's first Defoe.”
Bunyan wrote about 60 books and tracts, of which The Holy War ranks next to The Pilgrim's Progress in popularity. A passage from Part Two of The Pilgrim's Progress beginning "Who would true Valour see" has been used in the hymn "To be a Pilgrim".
The Scottish philosopher David Hume used Bunyan to illustrate the idea of a "standard of taste" in aesthetic matters: 'Whoever would assert an equality of genius and elegance between Ogilby and Milton, or Bunyan and Addison, would be thought to defend no less an extravagance, than if he had maintained a mole-hill to be as high as Teneriffe, or a pond as extensive as the ocean.' (Hume, "Of the Standard of Taste", originally published in his Four Dissertations (1757).)