Stand the book on a flat surface with the spine facing toward you.
Dip a knitting needling in a pot of craft glue.
Slip the needle into the opening at the spine of the book, where the cover has pulled away from the hinge.
Slide the needle up and down the crevice to apply the craft glue.
Flip the book over and do the same for the other side.
Place one sheet of waxed paper between the first page and the cover and another between the last page and the cover.
Stack three or four heavy books on top of the textbook and leave it to dry for 30 minutes.
Open the textbook and lay it face up on a flat surface. When open, a textbook with a partly detached cover will look like a flat piece of cardboard with a block of paper sitting on it. This is because the glue on one of the hinges has come away and the spine needs to be reattached.
Cut two pieces of duct tape, both 1/8-inch shorter than spine of the book and 1 and 1/2 inches wide.
Stick the tape to the glued side of the block of paper so that half of the width of the tape is covering the glue and the other half is sticking up in the air.
Bring the spine of the book up and press the exposed tape to the inside of the spine so the cover is attached at the joint. When you open the book now, a line of tape should be peeking through the crack between the cover and the first page, with the sticky side facing you.
Lay the second piece of duct tape over the crack where the tape is peeking through.
Remove the page or group of pages that have become detached from the binding. If you have a number of loose sequential pages, align the pages along all sides.
Apply a modest amount of craft glue to the edge of the page or stack of pages with a small paintbrush. Avoid excess glue getting onto either side of the paper.
Open the textbook and slip the pages back where they belong.
Press the glued edge firmly into the binding using a thin laminated card, such as a shopping club card, to apply pressure to the crevice.
Close the textbook and place a stack of three or four heavy books on top of it.
Leave the textbook to dry for 30 minutes.
Trim the edges of the newly-glued pages with scissors if they stick out further than the rest of the pages in the book.