Thought I might copy my comment here so it's a bit better organized as I think it might count as a new feature.
This would combine the "Want to Read: WHY?" and "private notes" requests in one.

When you click on "Currently reading" a new option gets added to the pop-up menu. This option currently only allows the reader to log how far they are in the book right now.

Instead, we could have "Reader's Journey" (trademark pending). This option would show when the book is added to any list. Without leaving the popup reader's can update how far they are in the book as well as add notes or a quote they like.
On the Journey page for the book readers can see all updates to reading progress and notes in chronological order.

An example:

Your Journey

09.01.2024

• Book finished
• What a ride, this book will def stay with me. I should thank seb for the recommendation

07.01.2024

• 85% read

06.01.2024

• 74% read
• phew, I really thought she would die, glad she didn't!
• Quote: "Sometimes time comes timely, time and time again" - Deandril Jones p. 245

05.01.2024

• 30% read
• Oh no! Not her.... can't stop reading now!

04.01.2024

• Not bad, nice pacing and character arcs so far.

02.01.2024

• Started reading
• Recommended by Seb to me.. He says I'll love the book, let's see...