Readers often assume a published non-fiction book has been independently verified. In trade publishing that assumption is usually wrong, and the reason is contractual rather than careless.
The contract places accuracy with the author
Publishing agreements typically contain warranties in which the author states that the work is accurate and does not defame anyone or infringe copyright.
Those warranties are backed by an indemnity, meaning the author accepts responsibility for consequences arising from a breach.
Once accuracy is contractually the author's obligation, the publisher has no structural need to duplicate the work with staff of its own.
Authors sign these clauses routinely, often without appreciating that they carry personal financial exposure if a claim is ever made.
Magazines developed a different model
Periodicals with checking departments built them because they publish frequently, on short deadlines, about living people and current events, with high exposure and no time for retraction.
A book is written over years by someone with deep familiarity with the subject, which is a different risk profile entirely.
Checking a full-length book line by line would also take weeks of specialist time per title, at a cost most trade books cannot support.
Legal reading catches a narrower set of problems
Books that carry legal risk are read by lawyers before publication. That review looks for defamation, privacy breaches, contempt and copyright exposure.
It is not a general accuracy check. A statement can be both wrong and entirely safe to publish, and the legal read will pass it.
What triggers a legal read is the presence of identifiable living people or contested allegations rather than the difficulty of the subject.
Editing catches some errors incidentally
Copy editors query internal inconsistencies, implausible figures and details that contradict something earlier in the manuscript.
This produces real corrections, but it depends on what the editor happens to know and does not amount to systematic verification.
A confident, internally consistent error will pass through the entire editorial process untouched, because nothing in that process is designed to catch it.
Where independent checking does happen
Academic presses use peer review, which examines method and evidence in a way trade publishing does not attempt.
Some trade authors hire checkers themselves, at their own expense, and the fact that this is worth mentioning in an acknowledgements page indicates how far it sits outside normal practice.
For readers, the practical consequence is that a book's reliability rests on the individual author's standards rather than on any process the imprint guarantees.