As you said, you have read for several hours, you must be got eye strains. It is a natural symptoms for people reading for a long time. Now, what you can do is to let yourself a good rest. Have a good sleep. Even if you don't want to sleep, you can closed your eyes for a while and let your eyes rest. Remember to take regular rest the next when you read books. Good luck!.
Well, generally speaking, it is normal to have that kind of symptom. First, you should make sure if the reading is the cause of your eyes. Because even if you are reading, there are also many reason which can cause your eyes become watery. And if your eyes are still painful after reading, it may be your eyes pressure which can cause this. As we know that when we read for a long time, our eyes have to focus on one point for a long time, at that moment, it will make your eyes feel stressed. And then have painful feeling. So, at this moment, you should probably read less and make your eyes have enough time to rest. And you also should better go and see a doctor so that they can give some treatments. On the other hand, you should know that infection and irritation can also make your eyes pain so much, so you'd better pay more attention to them too.
Maybe it is because the book was so close to you when you were reading, which will cause your eyes tired and pain easily. if so, you need to put the book a little farther from your eyes.
It may also be related to the light in the room where you were reading.Don't read in strong or weak light, it is bad for your eyes.
If you still feel pain after that , you are supposed to visit an eye doctor and a pair of reading glasses is a good choice for you.
Your eyes feel hurt because you read continuously for a long time with no rest which causes the eye nerves in an intense state. And you may read the book at a near distance which makes the eyeballs not adjust at a suitable pace. You should better stop reading and drink the chrysanthemum tea to release the tired eyes. Hope it will be beneficial for you.