If You Like The Eight by Katherine Neville ...
If you liked Katherine Neville's The Eight, you may also be interested in her 2008 novel, The Fire, and these titles:
The Overseer by Jonathan Rabb
Agent Sarah Trent and Professor Xander Jaspers search the globe for a missing 16th century manuscript that outlines a plan for world domination.
The Flanders Panel by Arturo Perez-Reverte
Who killed the knight? Julia, an art restorer, finds this inscription behind a piece she is working on: a 15th century Flemish panel of a chess game. As she gets pulled into solving the centuries-old crime, a contemporary killer murders anyone who comes close to uncovering the secret.
Moving Target by Elizabeth Lowell
"When you read this, I'll be dead ... " These are the troubling words Serena Charter's grandmother has written on a note accompanying four pages of a centuries-old illuminated manuscript delivered after the old woman's passing. Seeking clues to the mystery laid out before her, Serena turns to Erik North, a reclusive manuscript appraiser with a passion for the past.
A Season for the Dead by David Hewson
U.K. novelist and journalist Hewson (Solstice) presents the first in a line of thrillers set in Italy and features detective Nic Costa and an ensemble cast drawn from the ranks of the Rome state police.
University professor Sara Farnese is at her desk in the Reading Room of the Vatican Library perusing a 10th-century copy of Apicius's first-century cookbook De Re Coquinaria when former lover and fellow university professor Stefano Rinaldi careens into the room dragging a large plastic bag.
Rinaldi dumps the contents of the bagâ€"the freshly flayed skin of an adult maleâ€"and quotes the Christian theologian, Tertullian ("The blood of the martyrs is the seed of the Church"), then takes a couple of bullets in the head from a panic-stricken Swiss Guard. Detective Costa and partner Luca Rossi are outside the Vatican in St. Peter's Square on pickpocket patrol when they catch the news of the shooting on a police scanner, charge into the Reading Room and are quickly kicked out by security man Brendan Hanrahan for jurisdictional reasons ("The Vatican is another country"). Rossi and Costa become officially involved when the skinless remains of Sara's lover and the body of Rinaldi's wife are found strung up in an ancient Roman church. After this rousing beginning, the intricate plot spins off in several directions, involving corrupt cardinal Michael Denney, the Mafia, Vatican secrecy and the serial killer who's murdering Sara's former lovers in ways that mimic famous paintings depicting the martyrdom of selected saints. Outsized, eccentric characters, a complex story and an abundance of historical detail make this engrossing book more than just another cookie-cutter, religious-nut serial killer thriller.