[For some good info: look in the WIKI (top of the page) and on the main forum page:]
Thanks for your very helpful advice.
I've looked at Wiki and can see it will be helpful.
I might not have discovered what was behind that link for weeks as I'm having trouble navigating the site. The links (e.g. user cp) don't construe much meaning so it makes discovery a slow progress for a newbie.
From the posts in this forum I can see that I'll have to consider the format I use for my ebooks. I'm developing English language tutorials for Chinese people. If I don't protect my rights there could be a billion copies of my work within a few months of my first sale.
I used to think there was only one format but at least I'll get some knowledge so that I can make an informed decision about which formats to use.