Hi Worm
James Rollins is a good writer IMO, he writes adventure fiction & tech-thrillers in the style of Matthew Reilly, Jack DuBrul,Steve Alten, etc...
his strong point is that the environment is also a strong character by itself as seen in almost all his books
1] Subterranean = below the antartic continent
2] Excavation = In the indian pyramids[i don't remember whih race]
3] Deep Fathom = Below the pacific ocean
4] Amazonia = In the amazonian raiforests
5] Icehunt = In the artic polar cap
6] Sandstorm = In the deserts of Oman
Sandstorm is a kind of prequel to the SIGMA series, of which "Map of bones" is the first book
you can however read MOB before sandstorm as it is not a sequel per se but some of the characters in MOB have their origins explained in SS
and they are both fantastic reads so go ahead & enjoy them
ps: My personal fav are Sub-T, Excavation. Amazonia, SS & MOB, also if you wanna know more bout him then read this interview
http://forums.thebookforum.com/showthread.php?t=5575&highlight=james+rollins+interview[march+2005]