Don't try to read it start to finish like a book. Your eyes will glaze over before you complete 10% of the project.

Treat it like a reference book, in that there will be a certain feature that is of interest to you, so read the part of the code that pertains to that. That section of code will no doubt spark interest in another part, and that is probably what you would look at next.

You don't and very likely won't need to study all of the code in a project, just the bits that interest you.

Mostly using my eyes. Just posting due to being curious as to learn what motivates posts like this, what kind of answers do you expect? Or is it something else?