Popular highlights feature
One function that Amazon Kindle readers used to provide (and perhaps they still provide, but I don't have much recent experience with them), is to underline or highlight passages within a book that had been highlighted by several other readers of the same book. This tends to bring to the attention of the readers the portion(s) of the book that they are reading that others found interesting or significant. This could help readers focus on the most important portions of a book, at least those deemed most important by the "wisdom of the crowd" that have also read that book. The eReader or book could theoretically retrieve this information from the LRS to determine what constitutes a "popular" highlighted passage. One limitation of this feature is that not all readers highlight passages of a book, but perhaps training could alleviate this limitation. One risk of this feature is that not all users like to see highlights in their book, but this could be mitigated by allowing users to turn off the feature, thus making this an optional feature.