For a layman, what’s a good, accessible introduction to Camus’ work on absurdity?
You can't go wrong by reading Camus himself, especially "The Myth of Sisyphus".
In addition to Herman Hofman's recommendation to read Camus, here are a few places providing information about Camus and topics associated with him.
Aronson, Ronald, "Albert Camus", The Stanford Encyclopedia of Philosophy (Summer 2017 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/sum2017/entries/camus/>.
David Simpson's "Albert Camus (1913-1969)" in the Internet Encyclopedia of Philosophy.
The Wikipedia article on Camus may also be helpful.
All three of these articles provide bibliographies where more information can be found. These three sources, being encyclopedias, are also good for other topics besides Camus.
Having more than one source is good in case one finds one of the sources inaccessible or for some reason confusing.