Improve documentation

[oyooyo]

The documentation isn't very good right now. My english is inferior, information is missing or incorrect etc.

Any kind of help improving the documentation would be appreciated.

[AndrewSpec]

I have some changes for the polish hachette collection, add me to the project so I could push my changes.

[oyooyo]

Hello @AndrewSpec ,
I cannot remember that you have contributed to this project yet (correct me if I'm wrong), and I'm a bit hesitant to add someone to the project who is a complete stranger to me so far. I hope you understand that - after all, you could theoretically also be someone who injects malicious code as soon as I've added you to the project (even though that's very unlikely of course).

I suggest that you instead create 1-2 pull requests with your suggested changes first. If I then see that you are a trustworthy user who is indeed providing useful contributions to the project, I'll be glad to add you to the project.