Historical accuracy is judged more strictly when a production has invested heavily in historians. A book has to balance reader interest, useful evidence, and the limits of what fits on the page. Even an author's own book therefore cannot contain everything that author knows or believes. A film about the Tribal class could begin with the books by Alex Clarke and Martin Brice, but consultation could make its reconstruction more accurate. Published work serves as a starting point for further investigation.
Notable Point · 2:18:27-2:20:42
Why a naval-history book cannot replace expert advice for a film
A book can give a film a strong starting point while omitting details an adviser could explain in person.