Judith,
Karin Slaughter's books tend to be gritty but very suspenseful. I've followed her Will Trent series but haven't read any of her others. I'll add that one to my buy-soon list.
Lex,
The Tainted Cup is next on my list to read. Let us know what you think of it.
I read and loved We Are Legion (We Are Bob), the first book in the Bobiverse series by Dennis E. Taylor. His writing reminds me of John Scalzi's with serious themes interspersed with humor. The likeable main character was once human, and as the title implies, there are many versions of him. I'm looking forward to the next one in the series.
Right now I just started reading The God of the Woods by Liz Moore. A teenage girl disappears from her summer camp in the Adirondacks. Her parents own the camp, and history seems to be repeating itself because the teen's older brother disappeared 12 years before in similar circumstances. The search for her has just started, but already the plot is thickening because it seems that everybody has secrets they don't want revealed.