It is said that when novelists run out of ideas, they start to write about writing, and this tendency has threatened to destroy some of Jennifer Johnston’s recent fiction. Stella, in The Illusionist, confronts her new typewriter with “What is the next word to be? - What will happen when I discover that word?”, and Clara, in The Gingerbread Woman , messes around tediously with the keyboard on her Mac: “Click. Double click. Switch on. Cecclllmnm.”

The effects there were so vapid that the heart sinks when this latest book opens with the same solipsistic posturing, its internal author drawing out tortured parallels with God and allusions to Magritte. Get past this barrier, however, and what develops is a fine drama of family relations, chiselled from the bedrock of 20th-century Irish history and touched with an eloquence not seen in a decade of Johnston’s writing.

This is not a novel, indeed, but a memoir. Its author, Imogen Bailey, plunders a trunk full of old letters and journals to trace the evolution of her family over four generations, and to appeal to her brother, Johnny, whom she believes to be alive despite evidence of his death some 30 years earlier. What events led to the apparent drowning of this strong swimmer, once destined for the Olympics? How did the Bailey family unravel so traumatically from the knot of siblings gripped tight by Imogen’s great-grandmother, Louisa, and what catalyst drove Imogen herself into mutism, estranged from the remnants of her kin?

Partly it was scandal, the twinned sins of homosexual and adulterous transgression, but partly it was Time bearing down on a presence and a class, no longer required in Ireland . “We all disintegrated, disappeared, uncles, cousins, so many fled,” Imogen’s father recalls. “Why did they think they had to flee? What did they think they had done wrong?”

The strengths of this book stand out dramatically against the weaknesses of its three immediate predecessors. Johnston has returned to a flowing construction, to fleshing out properly the emotional and physical landscape her characters inhabit. Gone is the format on which she has recently relied so heavily: the fraught, stagey dialogues, interspersed with staccato passages of thought association and irritating snatches of song.

Here, she abandons theatricality for a cinematic gloss; scenes are lit and darkened in tune with the narrative mood. At the family dinner table under a hanging brass lamp, “our food and the table settings were brightly illuminated and our were in shadow; our hands, like disembodied creatures, moved in and out of the light, cutting, buttering, scooping and generally manipulating.”

The descriptions of Ballsbridge in the frozen winter of 1970 are similarly beautifully drawn, and the “grammar” of family relationships, as Johnston once termed it, fastidiously selected: when mother and daughter fail to embrace, and stand “angled into each other in silence”, the “angled” is perfect - this could be Lehmann or Bowen writing.

Better prose will shift criticism to other areas, however, and specifically to the question of Johnston’s historical sensibility. No one will complain, I think, about her somewhat clichéd contours of the first World War - after all, she claimed this territory long before Barker or Faulks. And the occasional “time-line” pointers of the plot - the family dancing at a wedding as Michael Collins dies - are forgivable in a book which condenses a century (though the careful chronology does go awry when Imogen, born in 1955, somehow turns 18 by 1970).

For all this, the past suits Johnston better than the contemporary, where her Edwardianisms, - men are invariably “cads” and people did in “motor accidents” - betray her.

But what does tug at the sleeve sometimes is the worry that individual elements of this story are over-familiar, jaded by previous deployment in the Irish fictional canon. The historical trajectory needs new spin, new interpretation, but one senses instead a passivity on Johnston’s part. Is she guilty of a kind of complacency? Has she done enough to recharge or even upset the standard narrative (and the academic audience which needs her to confirm it) of Anglo-Irish Protestantism Big House, Great War and Grand Decline?

It seems begrudging, though, to cast such doubts, while simultaneously praising the novel for its elegant treatment of this very theme. And the elegant treatment of theme is, of course, what Johnston’s readers will appreciate. This is Not a Novel marks a clean break from an awkward, insubstantial run of work, and with its well-finished narrative construction and decorous prose, it has the welcome feel of a good writer coming home.