The Mirror's Truth picks up right where BR left off and just proves how great a writer Fletcher is. He does a stupendous job writing from so many different viewpoints and his characterization is so deep. Every character is fleshed out across the novel and, if you read BR, all of your favorites are back and better than ever. Fletch also proves that he is very original with his world building, magic system, and monster creation (though I guess you can't have a fantasy novel without a dragon). My favorite part about TMT is the ability to get inside the mind of each character. It allows you to get a sense of each character's drive and purpose and just adds so much to the storyline.
Fletcher is at the top of my reading list and he needs to be at the top of yours, especially if grimdark fantasy is your cup of tea. If you like Mark Lawrence, you'll love Michael Fletcher. But do yourself a favor and pick up Beyond Redemption first. You'll be happy you did.