My cousin, in her second year of college, bought a second-hand textbook from a used book stall. Five yuan.

When she opened it, it was full of notes, densely packed.
Every page had them.
The handwriting was neat, even neater than hers.
On the title page, there was a name and a class: Civil Engineering, Class of '93, Chen Moumou.
She kept this book until now.
She passed the Level 1 Construction Engineer exam, the Cost Estimation exam, and the Geotechnical exam.
This book has always been with her, reluctant to throw it away.
Last month, she met an old master on a project.
The master saw her textbook and was stunned.
He asked where she got the book.
She said she bought it from a used book stall.
The master opened the book and pointed to the name on the title page, saying:
“This person, thirty years earlier than you.”
My cousin asked, “Do you know him?”
The master said, “He was my classmate.”
After graduation, he went to China Railway and built bridges in Guizhou.
Once, there was a landslide, and he didn’t make it back.
That year, he was only twenty-four.
He wasn’t married, had no children.
Only this textbook remained in the class.
He flipped to the last page of the textbook.
At the very bottom, there was a line of small characters she had never noticed before.
It read:
“If you sell this book to the next person, please leave the notes.
These notes are not mine.
They belong to everyone in our class.
During class, whoever understood it wrote down two sentences.
They’ve been writing for three years.”
He flipped a few more pages.
Pointing to a line of particularly cramped handwriting, he said:
“This part is what I wrote.”
My cousin placed the textbook on the table.
She told me she no longer looked at that book afterward.
It was placed in the middle of the bookshelf, like a tombstone, as a memorial.
She said, “I was able to pass because someone gave me a thirty-year head start.”
This year, she’s taking another exam for a new subject.
She bought a new textbook.
Only her name is on the title page.
She said it feels a little lonely.