In Russian textbooks, each word has an accent mark, because the accent affects pronunciation.
You won’t see any stress marks in regular books. But for the learning purpose knowing where the word stress falls is extremely important.

For example, there are 3 letters О in the word ‘молоко’, and only one of them (the last one) is pronounced like in the alphabet. The first two are pronounced like “a” because they are unstressed. Generally speaking, Russians don’t care about unstressed syllables and they pronounce them casually. If you do the same you will get the correct pronunciation without thinking too much.

It is similar to English, particularly American English when you hear: “I gonna do it, I wanna go” … instead “I want to do it, I want to go“.