Hard as Rock by Stephanie West

After the loss of her parents, Meline scrapes together the cash to take a once-in-a-lifetime trip. Armed with her great-grandfather’s journal, retracing her heritage should be exciting, yet she can’t shake the frightening feeling someone’s been watching her from the moment she arrived in the old city. Then Roc shows up just when she needs him, offering to help. He’s sexy-as-sin, wealthy, and well-connected, but there’s something he’s hiding.
Roc needs to locate his Khargal sire’s lost sigil before all hell breaks loose, and Meline holds a journal with the answers. After centuries of “liberating” art, he’s never thought twice about lying or stealing, but when the captivating woman appears at the site where his father’s buried, he hesitates. Something about her has gotten underneath his stoney exterior, and he doesn’t know what to do.
When a clandestine group hunting the sigil emerges, Roc and Meline must face them together before the sigil turns everything to ash. Yet the challenge may not be finding the sigil so much as breaking down the wall guarding Roc’s heart.