Yes, EPILOGUE is a Scrabble word!

Letter values in Scrabble US: E 1, P 3, I 1, L 1, O 1, G 2, U 1, E 1.

Is it a valid word?

EPILOGUE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a short speech (often in verse) addressed directly to the audience by an actor at the end of a play
a short passage added at the end of a literary work