Fuck books certain things are most valuable when you have a mentor whos done it, knows it works, put the time in and has the credentials to back it up. Videos at least have a better chance for you to learn something also you never know if you have to adjust the technique based on if you happen to mess it up need to adjust it, or if the person is drugged up for example. Don't even get me started if their is height difference weight difference scenarios, and different approaches to said scenario. You definitely want to invest money in the right people and places
(you have a mentor)
for others who can't have a mentor, books save from ignorance.
I do not know if there are some people with Slavic origins here but I know that in the 50s in East Europe, boys and girls learnt stuff about surviving at school (including stuff about weapons, like how to handle mines, ect), they studied on books and practice.