The book, "The Encyclopedia of Shells" has all of the limitations mentioned.
But it does have excellent illustrations and I bought it because it had at
least two species I had been unable to identify anywhere else.  He does not
include many cones or cowries, figuring they are well covered elsewhere.
But he does have some other, less commonly pictured shells.  So, if you have
some of the other general type books, this is a worthwhile addition.

Tom Eichhorst in New Mexico, USA