Have you already read Michael Crichton's books? They've got suspense and some have a bit of that "is it science or magic" aspect. He's most famous for writing Jurassic Park and creating the TV series E.R., but if you like Preston and Child, you might like Michael Crichton's:
- The Andromeda Strain
- Coma
- Congo
- Spehere
- Prey
If you like Agent Pendergast's skills, some of the new Sherlock Holmes-inspired books might appeal to you. Some feature a woman Holmes, some other characters from the Holmes universe. One by Mark Frost features Sir Arthur Conan Doyle running into a man just like Sherlock Holmes and some people out of Holmes's timeline, like Bram Stoker and Madame Blavatsky.
- Moriarty, by Anthony Horowitz
- Mycroft Holmes, by Kareem Abdul-Jabbar and Anna Waterhouse
- A Study in Scarlett, by Sherry Thomas (Featuring Charlotte Holmes)
- The List of Seven, by Mark Frost
If you like the occult or strange artifact aspect of the Pendergast books, you might like:
- The Club Dumas, by Arturo Pérez-Reverte
- Mr. Penumbra's 24-Hour Bookstore, by Robin Sloan
- Carter & Lovecraft, by Jonathan L. Howard
- Lovecraft Country, by Matt Ruff
- The Dante Club, by Matthew Pearl
- The List of Seven, by Mark Frost (listed again, because it has Doyle and the occult)