Abstract: The specification discloses a book index which has an index page adapted for permanent attachment to the body of a page of a selected book, color indicia carried by the page, subject identification means associated with the color indicia, transparent colored sheets keyed to the colors of the color indicia and adapted to self-adhere to the pages of the book selected for marking and to cover the pertinent subject matter desired to be marked extending to the margin of the page whereby the color indicia is visible when the book to which the sheets are applied is closed. The marking and indexing of passages of selected subject matter is done by affixing the index page to the forepart of the book, writing in the title of the subject in association with the color indicia and affixing the colored sheets to selected passages in the book and extending the colored sheets to the edge of the page whereby they are visible when the book is closed.