For more a more complete (though still brief) introduction to artists’ books, check the Wikipedia article.
Simply stated, artists’ books are works of art in book (or book-like) form. An artists’ book may be a unique, one-of-a-kind piece but it might also be produced in an edition. It may be letterpress printed using handset metal type or photopolymer plates but it might also be printed offset, mimeographed, photocopied, written by hand, or created using online self-publishing companies. It might incorporate unusual materials like soap, food, or LEGOS. Sometimes it’s produced as a codex and will look like a book but it might also be a scroll, set of computer punch cards, or sculptural piece. This wide variety of form makes a single definition hard to come by but in almost every case, the appearance and production of the work is determined by the artist.