Family memoir is a notoriously difficult genre to pull off  any hint of sentimentality, self-indulgence, bombast or fascination with ancestors not worthy of wider attention instantly repels a reader. However, the five generations of inhabitants of Hancox (and their very extended family) are too eccentric, too principled, too accomplished, too demented, too adventurous, too interesting  in short, too much of a gift to a writer of talent such as Charlotte Moore (sister of the Observer's architecture critic, Rowan Moore)  for any of these potential flaws to present themselves here.

Hancox, a redbrick Sussex mishmash of wings and extensions round a Tudor core, came into the family when Milicent Ludlow, a wealthy, single, 20-year-old orphan, bought it in 1888. But the story doesn't begin there. Moore goes back more than two generations further in a rich, digressive narrative sprawl in order to both contextualise the family dynamics and to recount the full, engrossing lives of her forebears.

Milicent's uncle, Ben Leigh Smith, was a famed Arctic gentleman explorer whose ship, Eira, sank, stranding his party near the north pole. After his safe return he married an orphan 40 years his junior. Milicent's aunt, Barbara Bodichon, was a proto-feminist, artist and political radical. She was a friend of George Eliot, and her French philosopher husband would spring naked from the rhododendrons to frighten visitors and maids.

Milicent's husband, Norman Moore (known as NM), was the author's great-grandfather; the only child of a single mother (journalist and educator Rebecca), he studied medicine at Barts and became president of the Royal College of Physicians. Prodigiously energetic, he was friends with Darwin, Kipling and Florence Nightingale, and had previously been married to Milicent's cousin Amy, Charlotte Moore's great-grandmother. The story of this first courtship survives in detail because NM, thought not to be a good enough catch (like many suitors of the Smith/Ludlow family), was banned from communicating with Amy. Instead, he wrote her an unposted letter every day; the only missive that got through was a book of Irish tunes with a coded message within its pages (Moore still has it at Hancox). NM would eventually win his prize, but within months of their marriage Amy was showing symptoms of the tuberculosis that would take her life.

Hancox the house is a living archive of Moore's family. Through the letters, journals, schoolbooks and graffiti that have accumulated, Moore has been able to plunge into the minutiae of her ancestors' lives and to shed light on the many objects they have left behind: three "Irish crystals" found under the stairs are discovered to have been a gift from NM to his mistress  and soulmate  Ethel Porter. Most affecting is the story of Gillachrist, NM and Amy's youngest son, who perished in the first world war and from whose death NM never recovered.

Thoroughly immersive, finely detailed, and peppered with Moore's wry, independent and humane observations, Hancox is a window into a different era and an introduction to a compelling cast of characters. It's worth reading not just for these but also for the skill with which historical facts are woven into an abundant narrative tapestry.