The series looks interesting to me. Is it just a straight up adventure game?
They're like better looking Telltale games: interactive stories with dialogue choices. The first game is a bit more game-y in that you have a limited power to travel back in time (especially with dialogue options) and there are some (simple) puzzles based around that.
LiS is the better game but I think BtS gets a bad rap because it was made by a different developer. I still enjoyed it quite a bit and makes something that happens in LiS all the more devastating (BtS is a prequel).