I published a paper, and I've been receiving offers from various publishers to include the paper in open access books. What should I do please?
Be very careful about this. Many such emails are automated spam: people automatically scrape recently published papers and automatically generate such "invitation" emails. This mainly tries to get you to pay high "Article Processing Charges". Your paper may well end up in some PDF collection with completely unrelated stuff, which will not serve your academic career at all. (If the publication actually happens at all.)
I would very much recommend you only even reply to this if the email comes from someone you know, or whose name you recognize. If someone in the field is putting together a collection, that might be interesting. But even then you should try reaching out to that person using a different means of contact than given in the email (because any "contact information" in that email may well be fake), so find their institutional email address and ask them on that whether they are actually involved with this effort.
If this is just a canned spam email from some "publisher" you do not know, then just delete it.