Final answer:
Underlining about 10 percent of the text while reading is generally a good practice to highlight key information without overmarking the book, facilitating easier review and comprehension.
Step-by-step explanation:
When marking a book, the goal should not be to underline as much as possible, but to highlight and annotate key information and ideas that will be useful for understanding the text or for future reference. While there is no one-size-fits-all answer, many people find that underlining about 10 percent of the text strikes a balance between marking important parts and keeping the text readable.
Overmarking a book can make it difficult to locate the truly relevant passages later on. The focus should be on interactive reading; this includes using margin notes to summarize, ask questions, and react to the text. Effective note-taking facilitates recall and enhances comprehension, serving as a personalized study guide.
For instance, a character's pivotal decision or a thematic statement can be underlined, while side notes might contain personal reflections or analyses. Summarizing sections of the text in the margins or using drawings can also deepen your engagement with the material. It's about quality of interaction, not quantity of ink on the page.