I am not sure if you are asking questions or making comments.
You have discovered the main point, that the check mark in the content server means that the book is already downloaded. If you start downloading several books and are fast enough to start several before they previous ones finish then you will see a progress spinner on each book that is waiting to download.
Regarding download queues: you can long-press on a book to download it while another book is being downloaded, which means that something must remember that you asked for another download. The thing that remembers is the queue. Doing a "download all" is like long-pressing all the books in that category. All the books are queued.
As for help screens, that is a difficult issue. Every time we introduced a "help" dialog we get zillions of complaints that it takes too long, too many clicks, too wordy, get out of my face, etc. On the other hand we get zillion/1000 thanks for it. Maintaining that balance is very very hard. The world seems to be moving toward a "try it and see what happens" model, which is anathema to many people but exactly what many others want. For example, my wife doesn't use her phone or tablet because she cannot stomach the "try it" way of doing things. Unfortunately for people like her, the vast majority of users seem to prefer "tap and see", and in fact won't read any help or dialogs provided.