Eric Shanes’s remarkable book about the first half of J M W Turner’s career is the summation of thirty years of research into the painter’s work by a group of curators at the Tate Gallery, members of the Turner Society and Shanes himself. He offers a chronological narrative of Turner’s early life, sometimes proceeding week by week. Along the way, he traces Turner’s travels, homes, beloved fishing boats and exhibitions. Hundreds of paintings, watercolours and prints – many in colour – appear in tidy order alongside his text. His publishers (who have been aided by the Paul Mellon Centre for British Art) must be congratulated for the care they have shown. I have never seen a more thoroughly presented book about an English artist.

Shanes’s own research has taken him to dusty archives. In the Bank of England he found details of Turner’s considerable earnings and investments; he has also delved into 18th-century hospital records in search of Turner’s mother, who was committed to an asylum for lunatics in 1799. This frightful incarceration was kept secret by Turner and his father. They feared not only shame – Turner lived in ‘abject terror of being professionally compromised by public knowledge of his mentally ill mother’ – but also the discovery that they had lied about her condition in order to evade the hospital charges. The experience of mental illness in his family lay behind many of the less pleasant aspects of Turner’s personality, Shanes believes.

Turner’s passage from boyhood in the rowdy surroundings of Maiden Lane to professional affluence was rapid. What did he think about the world in which he wished to rise? Shanes boldly reappraises and even retitles a 1793 watercolour of Windsor Castle, which Turner magically transferred to an imaginary landscape with echoes of the Avon Gorge near Bristol. He calls this work Britain at Peace. Around the royal residence we discern a factory, farmland, a canal and a pack mule that, we are told, represents commerce. The spire of a church is visible. The sky is calm. But there is no sign of the military. Such is the ideal life of our island for Turner at the age of eighteen or so – hence Shanes’s title.

Whatever we think of this interpretation, it is certain that Turner was a fine artist of peace or, often, of peace threatened. Such is the theme of many of his landscapes. However, his marine paintings tell us that the deepest conflicts are not with national enemies but with the sea itself, in which frail boats are helpless when faced with the high waves of storm. Turner was the first marine painter to depict the waters as heavenly or demonic.

When did he first excel as a mature artist? Perhaps with the magnificent Battle of Trafalgar of 1808, which treats that conflict as though it were a clash of metaphysical forces. Turner was then in his early thirties, yet painted like an old master. Indeed, he was always old before his time. He learned his craft very quickly, as though there were no one who could teach him anything. By the second decade of the 19th century Turner had begun working on incomparable paintings that, with their classical aura, seem to be from another time; towards the last quarter of his long life, he produced paintings that seem beyond time itself, among them Peace – Burial at Sea, The Fighting Temeraire and even Rain, Steam, and Speed.

His first Continental tour, in 1802, was crucial to his development. In six weeks Turner travelled through France to Switzerland and the Alps before returning, twice sojourning in Paris. Here was his modern corrective to the grand tours of previous aristocratic generations. Turner saw and was nourished by all sorts of peasant life in the fields of France and the mountains of Switzerland. He became not only an English patriot but also a thoughtful observer of all he encountered in Europe, rueful of poverty, sympathising with half-understood manners, inspired by life beyond his native beaches.

One experience of the 1802 tour is not fully explored by Shanes. After the Treaty of Amiens, Paris harboured hundreds of paintings collected from different theatres of war. There were Poussins, Rembrandts, Titians and Raphaels, and dozens of artists and paintings that had never been seen in Britain. Turner looked at them for about ten days. Was that enough? Was it then that he decided that he could give his views on the world only through landscape? And was it in Paris that he shed his inherited Christian beliefs and embraced a world that the old masters had known, peopled by gods that had existed long before Christianity?

A few of Turner’s early canvases are purely figure paintings, and these are certainly the equal of those by Turner’s friend David Wilkie, the significant figure artist of the day. But Turner chose not to concentrate on human life. He had a wonderful substitute. Turner was a great artist of seafaring life because his boats stood in for people. He could glancingly convey sailors, from admirals to fishermen to cabin boys, but these were no more than inviting glimpses. The humanity of Turner’s art lies in his ships and their fortunes, whether at peace, at war with other ships or struggling for survival under inclement skies. In Turner’s art, boats take us from boyhood to death.

Turner’s study of shipping (and his love of fishing) took him to all sorts of harbours, ports, rivers and streams. Their wateriness, lit by the sun, clouded or frosted, found its way into Turner’s watercolour technique, as though there were a whole natural world boxed in the small kit of brushes and paper he carried on so many expeditions. Wateriness was his element, so it’s little wonder that he was no lover of sculpture. At heart, Turner preferred rivers, which are made by gods, to roads made by men.

Turner’s complicated patriotism was that of an islander with wings made from sails, and his religion was that of a traveller in time, measured in centuries or aeons. Shanes (rightly) detects some bright Christianity in an early picture of Ely Cathedral, but it is certain that, in later years, Turner held a Graeco-Roman attitude to the fortunes of life. Often he added quotations from classical poets to his paintings. So, most recent Turner studies have believed, the painter must have been influenced by literature. And did he not write poetry himself?

Shanes’s discussion of the connection between the paintings and poetry is persuasive, and he is kind about Turner’s own failed amateur verse. We should remember, however, that Turner drew on the poets of older generations, not on the work of his contemporaries, and this influence added to the latterliness of his peopled landscapes. He could never manage the epic, except through the sadness that lives in memory. Often, memory was as important to Turner as new experience. True, there was one contemporary poet whom Turner admired: Byron. But Turner could never capture on canvas the ebullient, unexpected and defiantly controversial qualities of Byron’s verse.

Turner himself inspired no poetry (though he helped to form Ruskin’s prose, which was often as good as poetry) and was ignored by the Pre-Raphaelite artists who flourished as his life came to its end. He founded no school because he was inimitable. Art education was, however, important to him. His knotty lectures as the Royal Academy’s professor of perspective are well reconstructed by Shanes. ‘But what about aerial perspectives, and the undrawable perspectives given by cerulean blue and gold in your own paintings?’ a student might have cried. The most beautiful aspects of Turner’s art could not be explained in a lecture.

Admirable though it is, Shanes’s book ends with a warning I find disturbing. To understand Turner as Shanes does, future writers must possess ‘the correct cultural mindset’. I think Shanes still has much to prove about his own views on culture. In particular, he will have to match himself against Ruskin, who has only one tiny, unindexed mention in this book, but who was certainly the greatest critic of Turner that we have ever known and who, correct or not, was never constrained by a ‘mindset’.