I've read a lot of books. Enough to say that there's always a problem in a good story that is eventually solved. I had to read an American Childhood over the summer and, sadly, I hated it. Nothing happened! Usually when I read a memoir it's about an event, but An American Childhood, was well, a normal american childhood. Why would someone write a book where nothing happens?
I will try to answer this, knowing very well that many share the same analysis of Dillard's work. I seek not to change minds, but rather offer a potential morsel of explanation. I think that part of the reason why a reader might feel that little transpires in Dillard's work is because of the manner in which it is written. It is memoir based, but is similar to Joyce's Portrait of the Artist as a Young Man in its playing around with the idea of consciousness. Dillard seems to be presenting a collection of images, mental frames of reference that played a vital role in the formation of modern identity. In presenting her life in such a manner, Dillard is reminding the reader that consciousness is not singular with a directed and teleological end. Rather, the emergence of identity happens as a result of one experience merging with another one and that the construction of one's sense of self is often a disjointed process where different ideas hold different sensations of meaning. It is a challenge to read a work like this because of the absence of this structured end, primarily because consciousness and maturation themselves are not structured. Rather, events happen, and like seeds tossed, some of them germinate into a new conception of self and sometimes little, if anything, results. In describing this sense of consciousness and Dillard's style, one can see its philosophic implications, such as in the ideas of self consciousness put forth by Daniel Dennett:
Dennett points out that human consciousness is full of gaps ... further, what seem to be images in the “mind’s eye” are nothing more than the various computations produced by the brain. The brain does not turn on a blue light in any Theater of Consciousness when one thinks of the sky; rather, the subjective sensation of blue is nothing but the computations of memory circuits.
I think Dillard's style of writing where it appears "nothing happens," is because she believes that her identity was constructed in a way where there was no specific narrator or structural force that guided it. Rather, some events happened and some experiences resonated in her "mind's eye." As she went through it, unaware of results at the time, her style of writing is an attempt to allow the reader to feel the same experiences of confusion and wonderment that she herself experienced, the telling aspect of a memoir.
One other reason which might explain "what happens" in Dillard's work is another explanation from Joyce. In his work, Ulysses, Joyce suggests that the greatest of journeys and the most intense of voyages might not necessarily result from sailing over oceans, or treks across ancient lands. Rather, the most relevant of quests could be the result of daily life. The heroic quest is not one against monsters in far off worlds, but rather lies in daily exploration of one's self. In its absence of a formal sense of structural narrator, perhaps Dillard's memoir operates in the same way. While one can read it as "nothing really happens," perhaps this becomes Dillard's essential point that in random events that are taken as a standard part of life, the most profound senses of change and maturation can develop.