Amazon Kindle Unlimited is a subscription with a monthly fee and you get to read a selection of books without further cost.
I have just realized the value of it when I searched "British Military" in it:
https://www.amazon.com/s?k=british+military&i=digital-text&rh=n%3A133140011%2Cp_n_feature_nineteen_browse-bin%3A9045887011&dc&ds=v1%3A148rD%2FFBGYyGIYUUQDosItNpJCUs6nrJivyltVrfv5Q&crid=3DDXWCL8Y49EX&qid=1781216927&rnid=9045886011&sprefix=british+military%2Cdigital-text%2C162&ref=sr_nr_p_n_feature_nineteen_browse-bin_1
24 pages of books in good variety. I think I'll stick with it.
Anybody else having it?