The Problem with Diary Entries in Novels

I have been reading Parable of the Sower, by Octavia Butler, the grand-dame of science fiction, recently and I have a problem. The plot is fine. I would describe the book as a less-than-exciting Dystopian. No the plot or the characters aren't the problem, the problem is how the book is put together. You see, Butler writes each chapter as if it were a diary or journal entry. Each chapter starts with a quote from a book called "Earthseed: The Books of the Living" (which is another problem), but then the chapter will start with a date and off we go with our diary entry.

Now, I kept a journal religiously for two years and if you are writing a journal or diary entry, you are going to adopt a style of writing that tells rather than shows the reader what happened during the course of the day. You diary entries are reflections on past events, you are summarizing rather than using narrative to show the reader what is going on. And herein lies the problem with Butler's work. Often, in the middle of her chapters, she will launch into narrative and it really is jarring. One will read pages of descriptive summary, but then all of a sudden we are watching the characters have a conversation--complete with dialogue, dialogue tags, and beats. Here is an example from chapter 17:

"People on the highway, shadowy in the darkness, had begun to reverse the flow, to drift northward to find a way to the fire. Best to be early for the scavenging. 

'Should we go?' Zahra asked, her mouth full of dried meat. We built no fire tonight. Best for us to vanish into the darkness and avoid guests. We had put a tangle of trees and bushes at our backs and hoped for the best. 

'You mean go back and rob those people?' Harry demanded. 

'Scavenge,' she said. 'Take what people don't need no more. If you're dead, you don't need much.' 

'We should stay here and rest,' I said. 'We're tired, and it will be a long time before things are cool enough over there to allow scavenging. Its a long way off, anyway.'"

I mean, what is going on. This cannot be a diary entry. This is the author showing us what is happening to her characters. The thing is, I actually prefer this style of story-telling to summarizing what happened to a character. Show me what is going on through scenes and dialogue and description rather than just tell me. I guess the problem I have is that Butler isn't consistent. If you are going to adopt a diary-like style, then it should read like a diary entry. If not, then don't put a diary date at the beginning of each chapter.

Finally, the problem with the quotes from the Earthseed book at the beginning of each chapter. Early in the novel it is revealed that the main character is writing these sections of the Earthseed book. It is a philosophy she develops and then publishes later on. It seems like she later gains a following and almost starts a new religion? But here is the problem inherent in these quotes. Because it is revealed that the main character is writing these later in life, it ruins any tension that this book would have had. I know that the main character isn't going to die because she can't now--she has to live to write these silly Earthseed quotes. It is just like why I hate Harry Potter books. When you know the main character cannot die then there is no tension in the novel.

I really wanted to like this book, but I am considering dropping it.