the keyword
Not series="bar"
For a good look at what a search
could be: In the tag browser, series section:
Click once on the first series: (
HOLD Ctrl for the rest)
Click 1 time on each other series
you want (a Green+); Click 2 times on those you do not want (Red -)

One more thing that may make a difference: any / all search mode (there is a small tool icon at the bottom of the Tag Browser : ON that, the magnify glass icon. )
Or you can change the
or to a
and in the search bar
Code:
series:"=Elfhome" and not series:"=The Elven Prophecy"