I like to save to disk just because I'm a creature of habit.. If you try to save one of your books to disk you'll see what I mean - you need to tell Calibre how you want your naming of files to be.. I use this....

{authors}/{authors} - {series} {series_index:0>2s} - {title} - {isbn}

so when I save a book that's catalogued it appears in eg

folder = John Smith
file = John Smith - book 01 - I's a book - 1234567890.epub

You have various permutations of that so it saves as FN LN with series without etc etc..

I save to disk only because of just in case disaster and for whatever reason you loose formatting or whatever in Calibre, and like I said Im a creature of habit I just like to see the files named in a meaning full way for me.

For importing books I use a solution I found in these forums

^(?P<author>[^-]+)(\s*-\s*(\[?(?P<series>[^-0-9]+)\s*(?P<series_index>[0-9.]+)?]?)?)?.*?-\s*(?P<title>[^\]{[()]+\w)\s*-s*(?P<isbn>.+)

Which of course you can customise to suit how calibre reads your files before adding them if you have any books without metadata in them, as you can have Calibre import by using the file name or looking in the metadata.

Personally I like seeing the isbn number in the file name which generally reduces any ambiguity when searching for a book, having said that there are multiple isbn numbers for the same author and book depending on when and who released it (I'm assuming that any ways).

As far as the & I've only just realised that Calibre adds that as a separator for multiple authors or people credited to one book (I know I'm slow at picking up things at times :P)..

The reason I wanted to search for the & was to find the multiple authors and deleted the secondary author just to be able to keep my series under the primary author in one directory.... I'm sure there will be some laughing at this as theres probably a solution for it but till I fall over it and have someone correct me in my procedure thats the way I do it..

Again being a creature of habit I really hate having multiple authors because it doesnt sit well when saving to disc looking for a series in different places.

If it were possible and it probably is "Hopefully someone can put me right on this" I wouldn't mind if Calibre saved to disk a book twice once under the primary and second time under the secondary Author.

So when I look for a series manually Ill find it where it belongs and in an alternate place if need be..

Hard drive space is rarely an issue nowadays being a lot cheaper that what they used to be.

Cheers and avagreat day