Moon Lovers: Scarlet Heart Ryeo (book 1)

During a total solar eclipse, a 25-year-old 21st century woman, Go Ha-Jin, is transported back in time of Goryeo Dynasty.

She wakes up in the year 941, in the body of Hae Soo and there, she encounters the many royal princes of the ruling Wang family.

She initially falls in love with the gentle and warm 8th Prince Wang Wook, and later Wang So, the fearsome 4th Prince who hides his face behind a mask and is given the derogatory label "Wolf Dog." Meanwhile, rivalry and politics ensue among the princes, in a fight for the throne, as Hae Soo finds herself unwittingly caught between it all.