Ask HN: How do you effectively read code from someone else

What are some of the techniques you use to read and understand a code base from someone else, say open source libraries, frameworks, etc.

Do you just do lists (bullets of functions, etc), maybe mind maps?, abstractions? or do you just straight up top-down read it and get it.

I found that this is sometimes not an easy task since keeping track of dependencies and/or async flow is not a trivial thing. I personally just try to abstract as much as possible and then go deeper into each part (as needed), but maybe you have a better method.