A copy of a book sent out for review by the publisher to the press, booksellers, and others in order to attract attention to the publication.
Frequently review copies will have slips of paper inserted into the book, or have it written on the cover, announcing it as a review copy.
Textbook review copies are also known as “desk copies” or “instructor copies” and are given to instructors to review for consideration for adoption of the regular edition.
See also Advance Reading Copy.