The Earth God shrine in Hong Kong is not built to be noticed. A small altar stands by the door of a shop or a flat, assembled from cheap prefabricated parts and kept with whatever offerings the household can spare. Michael Wolf first registered these shrines as peripheral figures at the edge of his extended Back Door series. Once he had seen them, he saw them everywhere. Small God, Big City, published by Peperoni Books in 2013, moves them from margin to centre.

Wolf’s approach is patient and level. Doorway, alley, kerbside, the foot of a tower block: each shrine is photographed frontally, with the same deliberateness he brought to the cramped corridors and interiors of his other Hong Kong work. Nothing is dramatised. The gods may be made from cheap materials, the offerings modest, the passers-by indifferent. The camera insists on their presence regardless, and on the fact that they persist within an exceptionally crowded and thoroughly modern city.

The book is more than a run of pictures. Lee Ho Yin and Lynne DiStefano, both closely associated with heritage conservation in Hong Kong, contribute an interpretive essay that places the Earth God in the context of contemporary urban life, and interviews with several shrine custodians allow the people who tend these altars to speak for themselves. The 2013 Peperoni Books hardcover runs to 123 pages and carries its text in German.

For collectors, the interest lies in the conjunction. Here is a photographer whose Hong Kong projects form a coherent body of work, devoting a whole book to a single theme, and treating the small shrines of a rapidly redeveloped city with the seriousness of a sustained series rather than a curiosity. The book is now out of print, which will matter to anyone assembling Wolf’s Hong Kong titles; more decisively, the essay and interviews make it a record of belief and daily practice as much as a photographic album.