I've downloaded a book to Calibre, in, apparently, a format called ACSM - I know no more, as it doesn't give a title! And it's very small, 0.00 MB...... What's going on here ?

Don't know where/how I got whatever it is or why, but it would be nice to know what it is - although the contents don't look promising, do they....
[ I did google ACSM , but really didn't understand any better, apart from the fact it could be Adobe related..... ]
I've also a Complete Works of George Eliott in my Calibre Library, which says it's format is MOBI - but it won't actually load to my Opus. It does, interestingly, give it a nice green tick to say it
is on the Opus - which it isn't.
On both of the above, I have a Adobe a/c, which does recognise the Opus fine, if that helps, and has worked with a couple of other books.