I have had a PRS600 for around a year now, and use Calibre to manage my library and transfer books to the reader. The collections page on the reader groups books by both Tags and Series.
I have been asked to put some books on a new prs600 just purchased at a knock down price (obsolete?) this reader groups books by Tags, Series and Author.
Is there a way of stopping it from using Author, as it leads to a very long list, and Author sort is available on the title page anyway.