In terms of amount of light, it depends on the bulb you use - regular bulbs maximum wattage is 40, but for LED bulbs (we strongly encourage the use of LED), you can go all the way up to 150 watts equivalent. So, you can put a powerful bulb and you will not have any problems reading under it.

However, because the glass is clear, a powerful bulb will be too bright to look at straight on. If that is a concern to you, you should choose a fixture with glass that is not clear (see-through). For example, this product works great with high power bulb for reading, yet is not too bright to look at:

https://www.houzz.com/products/mini-pendant-light-handblown-brushed-nickel-finish-shade-clear-prvw-vr~124124033?lid=92469141