The population is divided into three categories of persons:
-The Changelings, shapeshifters very body language. They have long been regarded as little more evolved than animals because of their primal instinct but it's actually very strong people, listening to their intuition.
-The HISP, a human category that has developed powerful psychic powers (telepathy, telekinesis ...). Become extremely cold for a protocol, named Silence, was established a century earlier to condition the entire population psi (especially children) to feel no emotion, initially to eradicate the feeling of anger and therefore violence, but in the end, that they have total control of their being.
-The Human: population devoid particular strengths, wedged between the power struggle between the SPSI and Changeling.
Beyond the romance that I really liked was all the mythology created by Nalini Singh is exciting. This world is not so distant from ours and we find very interesting parallel.
The really exciting idea of the author in my opinion is the creation of PSINet (a virtual space where all HISP are connected in one way and another). This psychic relationship between each individual is very rich. There is something fundamental in the appeal of this series.