As I Lay Dying is one of those titles that all readers of literary fiction get to sooner or later--for good reasons. Not only is it one of Faulkner's most accessible titles, it is also very quickly read and less dark than some of his other work; some of the novel's developments are, however, told with black comedy/gallows humor. 
 As there are plenty of title summaries available here, I'm not going to bore readers with another one. I would, however, like to speak to some of the negative criticism this title receives--if that dissuades some readers, so be it; better to not attempt a title than to be disappointed by one--and, yes, I do realize the possibility of running off a potential reader who might otherwise like a title; all I can do is hope that I don't do that. If nothing else, I might prevent a couple one-star ratings and reviews of the 'boring' or 'confusing' or 'hated it' varieties. Those reviews always strike me as shoving a big extended middle finger into the faces of readers who do like a particular work. 
 Multiple narrators can be confusing--learning numerous characters at the same time, especially at the beginning of novel often is. In this case, it seems to me, helpful to remember that Faulkner isn't introducing a family--he's introducing members of a family--and what better way to do that than letting each tell his or her own version of the story. By that I mean, these are individual stories (narratives) about individuals; they describe how each family member sees him- or herself, how each sees their relatives, and how others, outside the family, see each and all of them. Collectively the narratives present the family and the novel. An aside, in As I Lay Dying, eyes matter--each character sees and is seen; all those descriptions of eyes are there for a reason. 
 Stream of consciousness is another aspect of Faulkner novels that some readers often find hard to understand. Creating a certain kind of confusion is often part of how the device works. Imagine, if you will, looking inside the head of another person--imagine being able to see his or her thoughts. Would you really expect those thoughts to be linear, punctuated, all neatly organized and processed? Wouldn't those thoughts more likely assume something of the shape or form of those of young Vardaman whose thoughts run one into another, unpunctuated, unorganized? Remember something else when you encounter this sort of writing--sometimes it's a way to slow the reader down, force a little more attention in a particular direction. 
 Faulkner is (in)famous for challenging use of punctuation, syntax, and grammar--his style. He's not afraid to use dialect, contrived words, or send you to the dictionary. This is not sloppy writing, or careless writing; he does what he does for a reason. The questions that should arise when reading Faulkner (or anyone else, e.g. Cormac McCarthy--considered my some to be the heir of Faulkner's style), is what is the author doing here and why? What does this sort of writing lend to the understanding of the story? Should I have paid more attention in rhetoric class? Why the hell did I not have a rhetoric class and how can I learn more about it? In the hands of an accomplished author, like Faulkner, it ALL matters. 
 Enjoy the book; have fun with it, as I think that was his intention.