You have to get nearly halfway through this book before it starts to show some life. Until that point, as Rowan Moore ambles in his wry manner through pages of familiar description of the capital’s built and social history, you find yourself wondering what it is all for. After all, if you choose to write a book about the architecture of London you are putting yourself in some pretty distinguished company.

Ian Nairn, say, whose magnificently off-kilter, beer-goggled 1966 hymn to the city, Nairn’s London, has been reissued as a Penguin Modern Classic to universal acclaim. Or Peter Ackroyd, whose colossal 2001 London: The Biography is drizzled with lazy assumptions but is an eloquent advocate of the city as living organism. Or psycho-geographer-in-chief Iain Sinclair, walking the city to awake its memories. And then there is the author who Moore quotes so often that his estate might dream of retrospective royalties: the Danish academic Steen Eiler Rasmussen, whose London: The Unique City of 1934 (first published in English in 1937) is a key work for architects, if little known by the public. Compile your own reading list on London, it will be a long and distinguished one. But to sup at this high table you have to bring something with originality and purpose to it. I can’t find quite enough of either in Moore’s book.

He is an excellent writer and critic for the Observer — a proper, engaged critic, not one of your preening narcissists. But as so often with us journalists, used to writing concise articles, he struggles to present a coherent narrative across an entire volume of nearly 500 pages. He divides his book into sections covering trade, public works, housing, planning, and (massive) population, each containing a number of sub-narratives. There is the sense of a loosely assembled collection of pieces strung together, of slightly forced links, of the lack of tight editing. He starts by describing London Zoo, and quickly you feel an analogy coming on, which duly arrives: ‘It is good for a city to acknowledge the beast in its nature and the possibilities of chaos over which its superstructures of enlightenment are built.’ Right now, he thinks that the acknowledged beast is too much in the ascendant. Let’s call this beast unbridled capitalism.

Vile buy-to-leave apartment towers snapped up by overseas investors? (Moore has a splendid phrase for these: ‘Lumps of speculation cast down from the computer of a time-starved architect’.) Our masters welcome them. Megalomaniac mega-basements for property wide boys and absentee oligarchs? Be our guest. Supposedly ‘public’ space which turns out to be security-guarded private domains where you cannot take a photo, let alone hold a demonstration? Look around you: these places are everywhere. Canary Wharf. Broadgate. Paternoster Square. Paddington Waterside.

All this has been dealt with in various earlier books by others — most notably Anna Minton’s Ground Control of 2009, which Moore acknowledges. But this is the point where his book finally gets a bit of fire in its belly, since Moore — a somewhat patrician type who, unlike his brother Charles of this parish, leans left rather than right — feels very keenly not just the shrivelling of the real public realm, but also the injustice of the social cleansing going on across the capital today.

He is right to. Much of the city is now unaffordable for normal Londoners, whether to buy or rent. Council estates within reach of the centre have been handed over to private developers who turf out tenants and right-to-buy leaseholders alike, weeping crocodile tears if they bother to weep at all. In their place come the usual ‘stunning’ developments of overpriced, undersized apartments which those evicted tenants and leaseholders cannot possibly afford. As Moore angrily points out, some of the most egregious examples, such as Southwark’s filleted Heygate Estate, where a long-established community was destroyed, are held up by politicans of both left and right as shining examples of ‘regeneration’. He sorrowfully observes: ‘The value of property skews human values.’ Of course London has been ruled and built by capital since forever, but it has also been a very variegated place. Now it threatens to become an investment-only monoculture, just as its population soars past its previous peak and is increasingly forced out to the very edges.

This has been stated often enough, but Moore gives some interesting chapter and verse: pity the hapless London borough of Southwark. Pity, too, Joanna Lumley’s and designer Thomas Heatherwick’s Garden Bridge project, justly excoriated here. And his (reported) descriptions of the city’s sex-club culture, including the leather-bar preferences of the out-and-proud former City of London chief planner Peter Rees, are reliably entertaining. But in the end, I still found myself wondering: what is the purpose of this book? It concludes with a manifesto which is really a wish list: more homes affordable to more people, simpler planning rules, fewer dumb towers, better planning departments. Apart from Moore’s opinion that parts of the green belt could actually benefit from being built on (a view now shared by many on both right and left), there is little to argue about here. He wants London to return to being a ‘slow burn city’ that renews itself through steady, planned change rather than being devastated as it currently is by rapid, ad-hoc growth. How to achieve this? The book concludes in a swirl of vagueness.