Alasdair Taylor's Answer

I understand that you would like to know whether you can use government documents in your book? That will depend upon the government, document and manner of use. For instance, you can use many UK government documents in a book as they are often available under the Open Government Licence (see v3.0 at https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/), which allows you to copy, adapt and re-publish documents, subject to attribution.