More exhausting than thrilling, Netflix’s latest period fantasy adventure, “Shadow and Bone,” will have a tough time breaking out of the fan base already built by the books on which it is based, written by Leigh Bardugo. It’s a show that never quite figures out its tone or audience, taking itself way too damn seriously to produce thrills while also being shockingly light on actual action. Worst of all, it often falls into a sort of tonal valley between more traditional YA storytelling beats and something aimed at adults like “Game of Thrones.” Clearly, Netflix hopes to tap the fan base for the latter, one that’s looking for a multi-character piece about good and evil across competing plotlines scattered through a magical land and is willing to deal with random powers, deadly creatures, and talk of foretold destinies. There are no dragons in this one, even if it could have used a few.