It depend so. The amount of trust I want to give. By citing an obscure book I can judge the fact "hm, that book sounds obscure, why isn't there some other source?" and then decide how much weight I give to it.

And if I don't have the book at hand I can identify the person who added the citation and can see what other edits they did to judge their domain knowledge.

No one does this. And Wikipedia myths spread to other media until it's hard to pinpoint where it started.

Sometimes referred to as citogenesis: https://en.wikipedia.org/wiki/Circular_reporting#Circular_re...

There is a list of known incidents: https://en.wikipedia.org/wiki/Wikipedia:List_of_citogenesis_...

But in case they do you can ask your other well established sleeper account for a book reference then reply a few days later with a: This is what I found posting. Then when asked you can point to yourself and say I've asked him. Do a conversation with yourself weighting how a book is hard to validate vs how important the information is to the article.