I recommend the book " The First Village of the Tang Dynasty " to you. The protagonist, Li Yuanxing, traveled to the Tang Dynasty before the Xuanwu Gate Rebellion and became Li Shimin's younger brother, Li Yuanba. He was conferred the title of King of Qin and began his life in the Tang Dynasty after marrying the princess. I hope you will like this story full of history and transmigration elements.