Reyes and Danika are my favorite couple in Gena Showalter's Lords of the Underworld series (followed closely by Scarlett and Gideon). I read this right after it originally came out and then just did a re-read. Really good! I had forgotten just how much was going on in this installment (#3). (We also meet William!) I think one could follow the story without reading the first two, but you would miss Reyes' and Danika's first meeting and seeing the shift in Aeron when he is charged with killing Danika and her family.
Intense, heart-breaking at times, and a great example of a human toughening up so she can survive in the world of immortals. Angsty love. And, of course, Showalter's trademark humor works so well.