Marking a book can help you notice patterns, remember useful ideas, and return to a passage without interrupting the pleasure of reading.
Use a simple color system
Choose a small number of categories before you begin. One color might mark language you love, another a practical idea, and another a question. A limited system stays legible and is easier to use consistently.
Write for your future self
A brief margin note can explain why a passage mattered at that moment. If the book is not suitable for writing, keep the note in a reading journal and include the page number. A few precise words are usually enough.
Create a closing note
After finishing a book, gather three things: the central idea, one passage worth revisiting, and one question that remains. This creates a useful record without requiring a full review.
Return before you collect more
Annotations become valuable when you revisit them. At the end of each month, choose a few marked passages and read them again. The goal is not to preserve every sentence, but to keep the words that continue to speak to you.