If the outside circle isn't showing, you just have to keep reading the book until it registers. Once your Sim tries to pick up a book they have already read, the option to reread the book will be there instead of the option to read the book.
In my experience, the progress circle completes once the book is read, but my sims will keep reading the book endlessly, while no circle is visible, until I stop them. I know they have completed reading the book when:
1. If I am reading it for an aspiration, the number of books read has increased by 1, and
2. If I click on the book in their hand as they are reading it, I get the option to "Reread..."
It's easy at that point to assume that reading the book was not counted because the number is added to the tally once the book has been completely read, NOT when the sim sets down the book.
So then, when you cancel the action so that they do set down the book, you don't see the number of books read increase, and most of us don't keep close track of what number they were on before they started that book. (Because that's the game's job, right?
Another thing to know is that reading skill books does count toward your tally of books read for aspirations, but ONLY the first time you read each of them. And, on top of that, it's hard to remember if you've already read a skill book unless you are watching that sim at all times and keeping a written list of the books that they read on a sticky note next to your computer.