What’s real, what’s not is half the fun in ‘Fake Blood’

“Fake Blood” is a clever hybrid of earnest first-person documentary, gory B-horror and metafictional mediation. Director Rob Grant’s slippery presentation muddles his point — if he has one — but it’s fun to guess at what’s a put-on.

Taken at face value, “Fake Blood” is about what happens when Grant…