"The most remarkable innovation in Mesopotamian civilization is urbanism. The idea of the city as a heterogeneous, complex, messy, constantly changing but ultimately viable concept for human society was a Mesopotamian invention. ... By the end of the third millennium, 90 per cent of the population in southern Mesopotamia was living in cities. By the mid first millennium, Babylon was the world's largest and only metropolis"
That quote comes from the six page preface, which, along with a timeline, a map, a glossary and an index, provides the only unifying framework. There's no overall conclusion and to a large extent the ten chapters in Mesopotamia: The Invention of the City could stand separately. Each looks at one city, running "in a roughly chronological sequence from fifth-millennium Eridu through to Babylon, which lasted into the first few centuries AD". In between those come Uruk, Shuruppak, Akkad, Ur, Nippur, Sippar, Ashur, and Nineveh.
For each city there's a brief history of its excavations.
"In 1856 members of the Royal Asiatic Society were told that a ruin site had been found in the remote desert region of southern Mesopotamia, huge in size and impressive in its height of accumulated debris. ...
Excavations resumed in 1928 to 1939 and again from 1953 to 1990. Although epigraphy, the study of texts, became another important focus after the discovery of archaic tablets in the 1930s, the archaeologists at Warka still concentrated on architecture. Considering that Uruk had the earliest, grandest and most numerous monumental buildings in Mesopotamia, it was well served by the enthusiasm and technical expertise of the German excavators. ...
Most of the archaeological information about Uruk therefore concerns either the early 'Uruk' period of the fourth millennium, or the later phase, especially the Neo-Babylonian and Seleucid epoch (the latter half of the first millennium)."
Leick doesn't get bogged down in the details here — there are sixteen pages of halftones, mostly of artefacts, but no excavation diagrams or stratigraphic sections.
In some cases the evidence is also, or even mostly, external.
"We have so far no archaeological record of [Akkad's] existence, no foundation deposits, no stratified sequence of debris, no architectural remains, no inscribed bricks to identify the site. All the same, the reality of Akkad as the new capital of a state founded by Sargon of Akkad has never been doubted because the name of the city appears in written documents from the second half of the third millennium from other Mesopotamian sites, quite apart from frequent references to Akkad in the cuneiform literature, omens and royal titles."
This is used to give an overview of the city's history. Leick then looks in detail at a few select topics, chosen for interest and depending on the vagaries of the evidence available, archaeological and literary. For Uruk, that's the development of bureaucracy and writing, the 'Uruk phenomenon' (the spread of aspects of Uruk culture across the Middle East and even further afield), and debates over political structures and the meaning of the 'temples'. For Ur, there's a look at some of the Ur III inscriptions and related texts: royal hymns, songs celebrating the king as the consort of Inanna, and a lamentation over the destruction of Ur.
Sippar had a gagam, a kind of 'convent' or secluded community of naditu women, whose archive has survived.
"Although there are isolated cases of a naditu seeking a wet-nurse, it is clear that the women in the enclosure did not have children. This greatly enhanced their chances of survival, since they were spared the risks of pregnancy and the debilitating effects of having to give birth...
While other women of the day passed their inheritance on to their husbands at marriage, the naditu could administer hers at her will. She was supposed to pass it back (with any accrued dividends) to her paternal family, but the documents make it clear that such conventions could be subverted by adopting a young girl to succeed her as a naditu and take care of her in old age."
With Ashur, Leick explores "the economic records of Assyrian businessmen and traders who had established themselves in a commercial enclave" in Cappadocia, nearly a thousand kilometres away. For Nineveh there's a more familiar narrative history of Assyria and its rulers from Sennacherib to Ashurbanipal II. And so forth, in a hugely varied smorgasbord of material.
Mesopotamia is scholarly in feel, situating what we know in the context of how we know it, and has forty five pages of notes and bibliographies (separate ones for each chapter). But its language is straightforward and not academic, and the presentation is lively, selecting material for interest and to provide context, rather than to argue a thesis or fill out a survey. It gives a feel for the diversity of Mesopotamian urban life over five millennia — and for the diversity of the disciplines and sources involved in understanding that.
Note: The Invention of the City is still relatively dense, and perhaps an odd choice as a cheap Penguin paperback; it would have seemed a more obvious candidate for a university press.