Order of Boundary Books

The Boundary series is a collection of science fiction/adventure novels written by Eric Flint and Ryk E. Spoor. The story follows paleontologist Dr. Helen Sutter, whose world changes when she examines a fossil discovered by a teenager in Arizona's desert. While she hopes this specimen might unlock some of Earth's most profound secrets, she never imagines it will launch her on an extraordinary journey to Mars.

Eric Flint and Ryk E. Spoor launched the Boundary series in 2006 with the first novel, Boundary. The series continues to this day. Here are the Boundary novels by Eric Flint and Ryk E. Spoor listed in their original publication order, which matches their chronological sequence:

Synopsis for Boundary: Threshold serves as the second installment in Eric Flint and Ryk E. Spoor's Boundary series. After her fossil discovery unexpectedly transported her to Mars, paleontologist Helen Sutter believed she had traveled farther than any scientist in her field could dream of in one lifetime. However, with a husband who works as a confident super-sensor specialist for a private space agency and connections to a former secret agent from the United Nations' Interplanetary Research Institute, Helen discovers her adventures are far from over. Her next stop is Ceres, an enigmatic asteroid, followed by an expedition to Jupiter's moons. Alien technology has sparked what appears to be the next "gold rush," and some are willing to ignite an interplanetary war to claim it!