I am trying to determine if Eigen 3.2.1 will be useful for my applications. Before using any package for my software development, I must have a thorough understanding of its underlying theory. I visited the Publications page for Eigen 3.2.1 at http://eigen.tuxfamily.org/index.php?title=Publications and found nothing under the Publications heading. I would think that a computational package as powerful as Eigen 3.2.1 would be supported by hundreds of technical publications. Where do I find them?

Eigen is mostly developed on spare times, and there is no such technical papers describing Eigen's magic. You can get an informal introduction through the slides of the slides of the CGLibs tutorial and ask specific questions here.