Traditionally, non-salaried reviewers get to keep the book they review. Some will in fact add the book to their personal library. Some will donate their review copies to libraries, prisons, schools, etc. Some will sell them to used bookstores for whatever they can get. Research the reviewers to whom you send review copies to insure that they are thematically appropriate to the nature of your book.
Book is accompanied by an effective publicity release or media kit.
Appropriate follow-up is performed for each review copy sent out. We have, in the past, listed numerouse web sites that are informative and extremely helpful to publishers, authors or anyone involved in the publishing industry.