King and Christie are both very good writers of popular fiction, but I expect that neither are typically considered by most professors of English Literature, to have written much that is particularly worthy of much literary analysis.
Assessment of the quality of “pop” fiction, is not only more subjective than literary analysis, but it has other criteria. It’s generally just not considered notably great literature at all, but can be judged within its genre as an entertainment product.
Some of the ideas from literary analysis can be applied to pop fiction, as a matter of interest and of assessing which such books might be a bit more interesting than others, but really one has to know one’s own tastes in pop fiction to know what one might want.
There is at least one pop Youtube dude who tries to bring some literary analysis to online discussions of pop fiction. And there are various others on the bandwagon, that talk about pop fiction in terms used with literature. But the bandwagon in particular often take ideas and over-apply them in weird ways. For example, the trend over the last several years for online discussions to talk about “arcs” as if plots and characters “having arcs” makes them great or not. Kind of like how in decades past, online discussions would argue about whether characters were 1D, 2D, or 3D.
So I’d just advise caution and moderation.
The best literature is great because it is so interesting that professors of literature (as opposed to casual online commenters) read it multiple times and write interesting things about it, for decades and decades.
There are also actual university lectures on literature posted on YouTube. Try searches such as “english literature lecture”.