I see you came to our site via the Brahma Kumaris one so you probably know that they have an online bookshop at http://bkpublications.com
Amazon's online sites have a wide range of books on spirituality including meditation.
For Buddhist meditation there are also many online book stores, including www.wisdombooks.com
More generally you could look at www.o-books.com and www.deep-books.co.uk or in the www.yoga.com online book store.
Most people probably get their meditation books via the organisation with which they are practicing eg. those interested in the meditation teachings of Paramahansa Yogananda would buy books online at www.yogananda-srf.org
If you have not yet decided on a particular form of meditation it might be helpful first to join some local classes or check out meditation books in the library to see what most attracts you spiritually. There are so many choices and sometimes it takes a while to find what best suits us.
