I chanced upon the book in a small bookstore．
我在一家小书店偶然发现了这本书。

　　chance on／upon: come across unexpectedly；meet by accident 偶然发现
　　再如:
　　I chanced on him last week for the first time in years．
　　上周是我几年来第一次碰到他。

I chanced upon the book in a small bookstore
I chanced on him last week for the first time in years．

I chanced on/upon the book in a small bookstore.
I chanced on him last week for the first time in years.

I chanced on/upon the book in a small bookstore.

I chanced on/upon him last week for the first time in years.

chanced upon 偶然发现

I chanced upon the book in a small bookstore.
I chanced on him last week  for the first time in a years.

I chanced upon the book in a small bookstore
I chanced on him last week for the first in a years

I chanced on/ upon this book in a large bookstore
chance on/come across unexpectedly/meet by accident

　　I chanced on him last week for the first time in years．
　　上周是我几年来第一次碰到他。

I chanced upon the book in a small bookstore.