From what I have gathered from my research, the secret of marketing a book seems to be to produce it in the right place to start from. It is really important that people know where to find your book, so it should be on Amazon, as well as listed on the bibliographical lists that libraries and bookshops use when selecting books.
If you want bookshops to stock your book really it should be available via a distributor: in the UK the two that all bookshops use are Gardners or Bertrams, and in the USA the company is Ingrams. So if you self publish, it is good to publish with a company such as Amazon CreateSpace or Lulu or Authorhouse who automatically make your book available via Amazon and get it listed in those important bibliographical databases (in the Uk the British National Bibliography and all books sold in the United States have to have a Preassigned Control Number which you apply for before the book is published and you can only apply if you have an address in America. So again, if you want Americans to buy your book, it is easiest to publish with a firm owned by Ingrams. see the Publisher Association's FAQ on the subject.
There are certain industry standards that all books must fulfil in order to be widely distributed by bookshops using the major distributing companys. Distributing companies list these on their websites but Lulu gives an example of such requirements.
If you publish with a company such as LULU they give you an ISBN so you don't have to worry about that, or they let you use a pre-existing one but that would not be included in their distribution listings so you would lose those benefits/gains.
I am going to a day conference: Troubador's The Second Self-Publishing Conference at the end of March  so that may enlighten me further.
Alison Baverstock's Marketing Your Book: an Author's Guide, ISBN 0713659653 London, A& C Black, 2001 £9.99 may be a bit dated but I am reading it to be going along with. It
contains the brilliant quote:
"I don't read books: there's not enough space in my life. When I have an empty space in my brain, it's cool, it's OK, I don't want to fill it with anything." - Celine Dion. Sunday Times Magazine, October 1999.
Which confirmed my suspicions.
One of Alison' suggestions is that the British Booksellers Association can provide a list of British Booksellers to whom to send publicity material.