Be aware that a downloaded Booki.sh book is stored in such a way that it can only be read using our software. You access the same URL, whether online or offline. This is a restriction imposed by the publishers, most of whom require us to apply DRM to their titles. We appreciate publisher concerns about uncontrolled private sharing of purchased ebooks.
Now, note that Book.ish acknowledges that this offline access still has limitations. The book can only be read 'inside' their own software.
Unfortunately, some vendors are touting Book.ish books as being 'DRM free'.
Here's what I think of when I hear the words DRM free ebook: I get a file that I can convert into another format if I wish eg from mobi to epub, and I can duplicate and give to other people to read on their ereaders. That is not what these vendors mean when they say DRM free. They mean access to a Book.ish style book which, in my honest opinion, you never actually 'own', you only ever 'rent access to'. So, caveat emptor.