[HarryT]

Personally I find author sort to be the most useful. I prefix the book's title with the series name and the number within the series using a Calibre "plugboard". That means that the author sort shows me authors in order, and series in order within each author.

I'm not sure if you're aware of this, but in author and title sort orders, if you tap the "page indicator" at the bottom right of the home page ("2/35" or whatever it may say) it brings up a search box which takes you directly to either a page number, or (much more usefully) to authors or titles beginning with a string you enter. Eg, if I want to go to my Agatha Christie books, I tap the page indicator, and enter "ch", then "Goto", and I'm at the start of the authors starting in "ch". For that reason, I don't use collections. I used to, but Calibre's plugboards give me a way of sorting my books which, for me, works a lot better.