Understanding Subspecies vs Species of Humans

[huginn]

I am trying to get a better understanding of subspecies vs species notably for humans. For example are Neanderthals a subspecies or separate species or if a new subspecies of Homo Sapiens were to emerge how would decide that there is a new subspecies
Is there a good book that explains this in layman's terms.

 

[Ryan_m_b]

A subspecies is a population of organisms that are the same species as another population but do not interbreed (or at least rarely) due to non biological reasons. This will eventually lead to speciation.

Further reading:
http://en.wikipedia.org/wiki/Sympatric_speciation
http://en.wikipedia.org/wiki/Parapatric_speciation