http://www.literature-map.com/
This is a fantastic site for helping to choose authors who are like someone you really like.
Just type in James Rollins and you will see authors who are close to his name on the map. The closer they are to the main author means that their books should be something that you would like.
I like James Rollins, Jack DuBrul, Douglas Preston, Lincoln Child, Steve Berry and have been told by member, cbell, that I would like Mathew Reilly also.
(Their names are all close together, so this map must be pretty good
)