I just ran into these spontaneously on the shelves at Shenendehowa, and I'm glad. Dina is a young girl (around 11) growing up in a sort of medieval society. She wants to have friends and so on, but the gift she inherited from her mother makes it difficult: anyone who looks into a Shamer's eyes will have to face all their own regrets and shame. Most people avoid looking.
The comparison to Tamora Pierce's books is probably apt: Dina is (mostly) capable and headstrong, but these seem a little darker, possibly because the enemy who has no shame is terrible indeed. Events often seem to be set against Dina and everyone else, before sudden reversals. The end of The Shamer's Signet seems especially convenient and out-of-nowhere. Oh, well.
Spiritually, they make me think of John 3:
This is the verdict: Light has come into the world, but men loved darkness instead of light because their deeds were evil. Everyone who does evil hates the light, and will not come into the light for fear that his deeds will be exposed. But whoever lives by the truth comes into the light, so that it may be seen plainly that what he has done has been done through God.
Almost everyone avoids looking in a Shamer's eyes. I have to wonder if I would, too.
I'm looking forward to The Serpent Gift and The Shamer's War, books three and four.