I'll continue observations here.
Sorting of books doesn't seem to occur until after you open one. You can sort by author, title or last read, but until the book is unpacked, the reader doesnt know where they belong. So it would likely not be too wise to sideload too many at once.
I loaded 70 books as a test run. As with many other readers, loading this many seems to be fraught. The app crashes at first and then when you reopen, the books appear as they ought to.
I think this one has a lot of potential but I'm not going to email the developer, I'll wait and see what happens.