So I Have Thought of You: The letters of Penelope Fitzgerald, ed Terence Dooley

Penelope Fitzgerald has a strong claim to be the least known great British novelist of the last quarter of the 20th century. This collection of letters casts little light on the creative processes that produced the distinctive fiction of her later years, such as her final masterpiece, The Blue Flower. She was, after all, notably reticent about her writing, remarking after one, slightly awkward, encounter with an interviewer that "He told me he found me a rather difficult job but the truth was I couldn't think of very much to say." But her letters do offer an essential guide, perhaps better than any biography could do, to the unusual trajectory of Fitzgerald's professional life as a writer, and to the diffidence which remained one of her most striking characteristics long after she achieved the kind of success which most writers only dream about.

Fitzgerald was 58 when, in 1975, she published her first book, a biography of the Victorian artist Edward Burne-Jones, and over 60 when she saw her first novel in print. After this late start, recognition followed swiftly. Her novel, The Bookshop, drawn from her experiences as a bookseller in Southwold in the late 1950s, which appeared in 1978, was shortlisted for the Booker. The following year, Offshore, set on a houseboat like the one on which Fitzgerald, her husband Desmond, and two daughters had lived, which sank along with many of their possessions in the early 1960s, won the prize. Fitzgerald's triumph, however, was underscored by the unpleasant sniping of male critics who hadn't expected her to win. In one letter she recounts her terrible Booker experience, which evidently scarred her for years afterwards, contrasting it to the stories she had read as a child about horses winning the Grand National when "everyone seemed to cheer".

Arriving at a television studio, "soaking wet because I'd had to be photographed on a bale of rope on the Embankment", she was met by the surly complaints of the presenter Robert Robinson, who asked his producer, "Who are these people – you promised me they were going to be the losers."

By then Fitzgerald was used to such putdowns, and all the more exposed to them because she never had an agent. One cringes with feelings of outrage and horror as her first editor, Richard Garnett, informs her that she is "only an amateur writer", or at the throwaway remark of Duckworth's Colin Haycraft which Fitzgerald took to heart, that if she went on writing fiction he didn't want it blamed on him, and that in any case he already had too many short novels with sad endings on his list. In the early 1980s, after a hostile review in which she found "so much personal dislike", she wondered "if it's a good idea to go on, if the going is to be quite so hard." Yet she remained resilient. One strand of correspondence details Fitzgerald's eventually thwarted attempts to write a biography of L P Hartley, against the "implacable opposition" of Lord David Cecil, who parades his letters from Hartley before her, but then shuts them up in his desk before she has a chance to read them. Another strand demonstrates her passionate desire to write something about the world of Harold Monro and the Poetry Bookshop in the face of a studied lack of interest from a series of publishers. Fitzgerald wouldn't give up, and in the end published an admired work of non-fiction about the poet Charlotte Mew, one of Monro's discoveries.

Terence Dooley, Fitzgerald's son-in-law, who contributes a well-judged, informative introduction, made the sensible decision, given the paucity of material for some periods of Fitzgerald's life, not to place the letters in chronological order, but in an arrangement according to correspondent. The first section of family letters, to Fitzgerald's daughters, Tina and Maria, are largely from the final years of Fitzgerald's marriage in the late 1960s and early 1970s, before her career took off.

The daughter of Edmund Knox, the editor of Punch, Penelope had left Oxford in 1938 with a congratulatory First, then worked for a time at the BBC. Her marriage to Desmond Fitzgerald, who won the Military Cross for heroism in North Africa, was overshadowed by his drinking and their financial problems. Even when their fortunes stabilise, life is lived on a shoestring. Penelope does "endless ticking" of exam papers as a teacher at Westminster Tutors, saves Green Shield Stamps, and resorts to dyeing her hair with tea-bags. She pines for her daughters, who have left home, and perceives the need "to justify" her existence. The wry, comical observation of her letters, from the most unpromising domestic minutiae of everyday life, leave one in no doubt that one is in the presence of a writer.

In later letters, she remains modest despite her growing distinction, and sometimes caustic at the expense of larger egos (one of Rushdie's novels is described as "a load of codswallop", while she questions the choice of Peter Ackroyd as Dickens' biographer as she can't see how Dickens' life can be written "by someone who has no sense of humour whatever"). It's difficult not to breathe a sigh of relief as Fitzgerald enters a relatively safe berth in her final decade. These wise and wonderful letters should provide a welcome fillip to her reputation.