I would call "Night of the Owls" a crossover, or event, but certainly not "MEGA-EVENT" like Blackest Night, Infinite Crisis, Civil War, etc.
It's a 5-part Batman story, and the other Bat-books (and All-Star Western) participate for 1 month (2 for Nightwing).

That's "only" 16 issues, compared to 50-70.

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