Translation:She advises me to read books whenever I feel sad.
in this case it's the same, but in another case "thấy" = "see" "cảm thấy" mostly used for writing and "thấy" is used for speaking.
"Thấy" is a special verb in Vietnamese. I can replace follow some verbs like see (nhìn thấy), hear (nghe thấy), smell (ngửi thấy), fell (cảm thấy)... "thấy" usually replace "see" but it may replace some verbs like feel, hear, smell ...
'she advises me to read the book whenever i feel sad' is not an acceptable interpretation. Any comment
Read the book would mean a specific book i.e. "The Book of Happiness". Read a book means any book.
Wah ? Bad advice... i always feel down when i just read something, especially after i finished the book.
When I wrote the translation I doubted between "when" and "whenever", wanting to satisfy DL. I found them both equally good. Sadly I chose the wrong one........ Was not accepted.