Document repair tape is discussed in a previous post. In general, it should only be used on books that are not too valuable or part of a special collection.
Make sure the edges of the tear are lined up correctly and apply the tape over the tear. Do not try to repair a long tear with only one piece of tape. If necessary, apply tape on both sides of the paper to attach loose edges but remember that this will add two extra layers of thickness to the book.
Archival tapes are usually 5/8 to 1” wide. Tape that wide can often be cut in half or thirds so as to lessen the amount of tape used in each book. In addition to saving money, it will also be better for the book. When tape is applied to both sides of a repair, cut the second piece a little wider than the first so the edges are offset.