Possibly reread where necessary, take notes or draw pictures, and ask yourself questions about what you’re reading. Really these two strategies are fused: you are moving just quick enough to keep momentum going and also just slow enough to permit things to cohere. Alternatively go slow and allow yourself to process and understand every beat. Reading comes in revisions and drafts, too: gradual approaches that recursively construct a model of the text.

(Maybe try to actively evaluate what “level” the material is - are you completely lost, or is it just a little elusive or is it “just challenging enough” etc.) You can make a note to look something up later of course, but especially on a first pass and first encounter with a work that might be or seem challenging, maybe just focus on the broad structure of the work, trying to understand as much as possible very quickly. Human culture belongs to everyone, and you don’t need to understand every reference to get most of the value out of a work. I would really suggest that in general don’t be worried about not being ready for a work, especially one as important and broadly relevant as The Myth of Sisyphus. It’s one of the great works of literature as well as philosophy, a cultural monument and apex and touchstone in its own right and it is as open to you as it is for anyone for an immediate encounter. Try reading it and see! There’s probably not a really satisfying answer for the general case.

Albert camus the myth of sisyphus