There is no definite answer to the question of how many pounds that a quarter inch of a glass shelf can hold. There are many factors that affect the answer. One is the density and the thickness of the glass. Very thin glass is normally more fragile than thicker glass. As well, glass shelves usually are held up by supports. The arrangement, size and strength of the supports affects how much the glass shelf will hold. If the glass shelf has weak supports, it is certainly not advisable to put a bunch of books on the shelf! It is best to read the manual or instructions of shelves that you buy in order that you can see how much weight it will take. Caution should be used especially with glass because if it is broken it can be very dangerous. If you want to store very heavy things, be sure to find a shelf that can take the weight.