These is My Words: The Diary of Sarah Agnes Prine, 1881-1901, Arizona Territories: a Novel by Nancy E. Turner (1998)
First, let me say I loved this book, eventually. . . and it is "adult fiction".
I borrowed this book on the spur of the moment a couple of months ago (July), and read the first few pages. They seemed rather depressing, and I didn't continue, partially because the book was due by then. However, a week or two ago, I was informed that the author goes to the church I've gone to the last couple of weeks. This book was nominated in 2007 to be the One Book AZ book. (By the way, I'd like to see Veil of Roses by Laura Fitzgerald for One Book AZ 2008!!) So, I tried These is My Words again. It is not easy reading. . . several people die in just the first 41 pages or so. However, by then, I had to know what happened. I have to say that this is the kind of book I've appreciated for years, since I was a kid (historical fiction in journal/diary format).
Wow, I was sorry when I reached the end of the book. Fortunately, there are sequals. There are several very sad portions, and some wonderful portions (for instance, I didn't realize the University of Arizona here in Tucson was the first university in Arizona) about the joy of reading and education. Sarah never got to go to school formally, but studies on her own, and eventually passes the 12-grade exams. She moves into Tucson with her husband, even though she hates being in town, so that her children could have the privilege of going to school. She runs a ranch on her own. Sarah is a very strong woman. If you go to the author's website, there are pictures of the woman Sarah is based on. Sarah is based on the author's grandmother's diaries and experiences.
An excellent read! I highly, highly recommend it!