Dear Emilio,
 
If you wish to identify common marine shells from the Venezuelan
coast, the following books are very good:
 
Abbott, R. T. 1974. American Seashells. Van Nostrand Reinhold Co. 630
p. 
 
Warmke, G. L.  and R. T. Abbott, 1961. Caribbean Seashells.
Livingstone Publishing Co. Pennsylvania. 348 p.
 
And specially: 
Diaz, Juan Manuel and Monica Puyana. 1994. Moluscos del Caribe
Colombiano. Un Catalogo Ilustrado. Fundación Natura.
COLCIENCIAS-INVEMAR. 291 p. ISBN: 958-95712-0-4
 
More literature is available but it is dispersed among several
technical papers. Access to copies of these books and papers can be
achieved through your friends that travel to the US or to Europe (or
by email, through CONCH-L, for example!). 
 
Systematic biology is a very complex subject, reason why there is
people getting PhD's and investing their professional lives in it! In
the same way, amateur collectors have consolidated many areas of
malacology investing years of patient and careful work and sharing
their collections and invaluable observations (and fun) with
scientists. In the best of the cases, experience from both people is
directly or indirectly put together in a book, for the enjoyment of
everyone. But writing a book on shells implies many years of work,
and not even after these years the product is perfect. Remember that
mollusks is the second largest group of metazoans on earth (and
bivalves and gastropods make the bulk of it), and knowledge about the
biology of mollusks increases day by day. There are books on shells
that are better than others, Their quality varies depending on
several factors, such as the researcher's access to literature,
access to other collections, experience, knowledge available on the
groups or on the locality that the book is intending to describe,
among many others. It is important though that the work is being done
carefully. The damage done by poorly done books or lists (written
either by amateurs or professionals) can be very misleading,
unpleasant, frustrating, and time-wasting (misconceptions, poorly
done interpretations about the biology of the animals, bad [really
bad] identifications, wrong reports of localities, etc.).
 
You see, Emilio, I think that _publishing_ lists can be problematic
if such work is not reviewed by a person with equal or more
experience or technical preparation than the author's. This problem
is analogous to publishing a book on the WEB. Some people believe
that the fact that they can write a technical book on the WEB makes
it very good because _many_ people can read it and can make comments
on it. For me, what makes good (more reliable) a technical source of
information, such as a book, paper or list, is not how many people
read it. It is better to know that the information has been reviewed
by people equally or better qualified than the author. 
 
Taxonomy (assigning  a name to a taxon) can also be a very
complicated matter, and it is not always related-to/updated with the
systematics of the group, although in the best of the worlds it
should be one of the products of the former. There are several rules
that have to be followed to define a name and to assign it to a
taxon. A good taxonomists has to have full access to lots of
literature, because part of his/her work deals on history research.
Carefulness of the researcher is also important. All these details
help on producing a name valid for many years (we all hope!) and
therefore, on stabilizing the nomenclature of the group. At the end,
what is very important is to have an idea (at least approximate) of
what we are talking about when we refer to a species, or to a
particular taxon. 
 
In some groups some taxa are easier to identify than others, and also
some species are more common than others. So, this means that the
latter have been collected more frequently and have been worked more
intensively than others. Then, their taxonomy is probably more
definite. But this is not always true. Careful reviews of very common
groups sometimes come up with surprises.
 
For rare shelled mollusks only a specialist on the group can tell you
more precisely (when possible!) the "correct" name of a taxon (when
available!), preferably if the group has been reviewed recently, and
if just shell characters are enough. Of course, accuracy on the
identification gets always more difficult when you get closer to the
species level. Not knowing what the name of a species is, happens to
everyone, amateurs and scientists for equal, and this is probably one
of the best excuses to go to meetings and talk to people, participate
of email discussion lists, and/or to be part of a malacological
society. 
 
So, finally, if you wish to start a list of Venezuelan gastropods
(this is great!), just start with few sources and use them
consistently. You will get (you are?) used to the fauna of your
preferred localities. It will be worth to add aside each of your
identifications the reference that you used for your final ID. This
will prove to be invaluable for your future work. Writing down your
doubts about the validity of your ID is also excellent to have on
hand time after the ID has been done. In the near future, when you'll
have access to lager collections, you will find among your notes very
helpful hints on how to improve and make more accurate your ID. With
time, you will gather more information about your preferred groups
and/or localities and you will become more knowledgeable on them. 
 
Let me know if I can be of any help.
 
 
Cheers,
 
Roberto