Sorting in Books is broken?

Sorting books within MacOs works fine. It is possible to sort on author or title but not so in IOS (iPad air). Sorting on the author ‘s name at first sight it looks ok: The surname is leading and the books are listed accordingly, but scrolling down the list suddenly books appear where the first name is leading. Alphabetically it’s right, but this is not a sorting you expect

Please let me know what your thoughts are about this, and how to repair the sorting function.

thanks in advance