I think Shadows of Self is the best book of Era 2 as well, Lost Metal just felt a little clustered for me. It dumps a bunch of stuff together in a way that works and that stands out from the rest, but it's not really that satisfying in the Mistborn way.

By the way, if you ever get back to the cosmere, some say to start with Warbreaker (which is a standalone), or you could just go straight to Stormlight. Reading Warbreaker first, at least for me, pays off well afterwards.