Back in 1975, John Berger and the Swiss photographer Jean Mohr produced an unusual book entitled A Seventh Man about the millions of rural migrants moving to western Europe to perform menial industrial labour. It fused poetic text, political analysis and striking images  one depicted a solitary figure on a horse and cart, having just left behind his ancestral land, slowly wending through sun-blazed dusty lanes in pursuit of a new life  in order to ask why those migrant workers are "treated like replaceable parts of a machine? What compels them to leave their villages and accept this humiliation?"

The images in Taiwan-born, British-based journalist Hsiao-Hung Pai's Scattered Sand are descriptive rather than photographic, but in every other way her book is a worthy successor to A Seventh Man. It focuses on contemporary China, where the scale of rural migration  over 130 million men and women have left their home provinces in search of work  makes the demographic debates about modern-day Europe seem parochial and hysterical. It pays tribute to a class of people that, although exalted under Mao as a revolutionary vanguard, has constantly to face the threat of pauperisation. It amplifies sounds  plaintive chants, desperate petitions, exhausted prayers, sceptical curses  that are often drowned out by the stentorian boosterism of the state loudspeaker.

Scattered Sand (its name comes from a dismissive term given to unorganised rural migrants) can be seen as an anthology of ghost stories. Its subjects, compelled to move by stagnant local economies and corrupt officials flogging off land to corporations, are invisible to many Chinese urban dwellers who have no interest in learning about the crowded shacks or cheap hostels into which they squeeze. In Fujian province Pai learns of men who toil in unsafe mines for the equivalent of 18 pence a day, risking lung diseases for which they can't be compensated because they lack work contracts.

And yet, what makes this book so important is that Pai rejects the all too common and deeply sinophobic assumption that China can only be described in quantum terms. It's commonly portrayed as too big, its recent transformations too vast to grasp, its population a muted and faceless army of drone labour. Pai, by contrast, treks to building sites few outsiders visit, wanders down side alleys to talk to the poor and the crooked, keeps in touch with her confidantes by letter and by phone over a number of years.

From these intimacies she shows her subjects not as ghosts, but as decent, quietly heroic men and women who sacrifice blood, sweat and tears to support their families. Literally so: in the "plasma economy" of Henan, a province full of underground blood clinics, she meets a peasant who sells his blood up to three times a day, in part to pay off a fine for having more than one child.

Injustices and indignities scream out of every page. Starting out in Moscow where around 50,000 migrants eke out livings in the face of skinhead violence, Pai moves across China  the brick kilns of the Yellow river region where child labourers are common, Sichuan where years after the 2008 earthquake millions live in temporary housing, the troubled region of Xinjiang in which anti-Muslim sentiment is rife  to present stories that run counter to the triumphalism of politicians, starchitects and speculators.

The book shines an uncomfortable spotlight on Britain too. After all, it's our desire for cheap toys and clothes to which many Chinese factories cater. It's our fondness for the freedom and mobility promised by laptop computers that fuels the profits of companies such as Foxconn at whose factories nets have been installed to stop workers jumping to their deaths. Are our labour laws perfect? A heartbreaking chapter in which Pai meets relatives of one of the cockle pickers drowned at Morecambe Bay in 2004 suggests not.

Scattered Sand does well to draw attention to the ways in which millions of Chinese people, in the face of physical threats and a censorious press, have gone on strikes and marches to protest against their conditions. Classic labour texts  A Seventh Man, Let Us Now Praise Famous Men  often privilege exploitation over resistance. Pai, diligent to the end, and writing out of love rather than hatred for China, holds on to the hope that resistance is fertile.