perhaps they are not helpful is because the books tend to
generalise, which strictly speaking is not entirely bad; but it
does trap the unwary reader.
ultimately one has to realise that they are dealing with an
individual, not some standard robot that came out of the
factory;
therefore communication is the only way to know the other party,
not some books telling you your friend's personality.
it is this whole thing on communication that these books usually
lack and rightly so, since the topic (and its associated topics) is
just too big to fit into one book.
most of the time, books provide the basic information, the rest is
usually up to the reader though.
listening skills, developing your self-awareness, honesty and
lying, social interaction theories are some stuff that are useful
to know. no doubt i have missed out some important stuff that i
dont know about, but i think these are good places to start
from.
asking yourself why you talk to the people you do is an interesting
way to start and so is asking close friends why they talk to you
:-)