And then had come the unlooked-for tidings of the imminent proceedings for divorce. And such a divorce! There were cross-suits and allegations and counter-allegations, charges of cruelty and desertion, everything in fact that was necessary to make the case one of the most complicated and sensational of its kind.
from http://www.eastoftheweb.com/short-stories/UBooks/UnkiBlow802.shtml
I think "one of" is used with "noun phrase".
e.g. one of the most famous mountains
But in this case it is used without "noun phrase".
Why?