If you're extremely bored, read them all.
If you need only the cream, then I offer:
Zack: You can't just roll some random encounter dice and tell your players, "Alright dudes, you're walking along the beach and you hear some praying. You look over and you see these manta rays in a church. Some of them look really pale."
And if you only want the creme de la creme:
Steve: What book did you find this thing in?
Zack: Steve, these are all from the Monster Manual.
Steve: No way, this thing isn't in there. What book did you really get it from? Fiend Folio? Some sort of Spelljammer book?