Hi,
DOnt know books which tells you about these stuffs, but the basic idea is this.
Near Field:
These are non-propogating components which are present in the vicinity of the antenna.
Far filed:
THese are propogating components. The present day tranmitter and reciver works on the far field components. The receive these propagating components.
But if you pertubrate the near field components by some means you make the standing invanescent waves (near field) into propogating ones. So the advantage of making these propogating ones is, the information which has been lost earlier in near field now could be obtained. Hence you have more information (near field + far filed).
Just an extra info, apart from antennas, this is active research topic in Imaging microscope. Earlier when imaging was done using far field components the resolution was in order of micro meters, now after pertubating near filed components you get extra info and would be able to resolve till nano meter level.
This area is called SNOM( Scanning Near field optical microscopy).
Hope this helps you.
Regards,
Thoppay