South London. 1915. Wag, the eldest of twelve in the eccentric, matriarchal Bourton family, sets off for war to escape trouble at home. After returning wounded, he embarks on a seemingly quiet career as an engraver and buys a house for himself and his enigmatic sister Ethel, who filled his thoughts as he was enduring war in the trenches.

Decades later, Wag's nephew Jack is also making his way in South London. After a short spell at Cambridge and a failed attempt to make it as a film producer, he finds himself a job reporting to the notorious Richardson Gang.

As Jack is drawn deeper into the sinister and sadistic gangster underworld, he discovers that his Uncle Wag's apparently tranquil existence may not be all that it seems. Although a generation apart, their paths are about to intersect...

Narrated in alternating voices by Wag and Jack, The Book of Wag is a richly woven portrait of South London at a wild, lawless time that has now passed. Part fiction and part family memoir, it draws on the handwritten, unreliable war journal by author Paul Sidey's own uncle, and other family stories. Dramatic, funny, tender and tense, it is the story of one family's journey through the ever-evolving landscape of 20th-century London.