So, I just finished the book...this drama did a good job elaborating on and mirroring from the source material. A lot of the dialogue came directly from the book.
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Some things that was changed: more screentime on the side characters in the drama (like 1, 16, LiJing, Xuan Nu, etc), perspective from different characters (the book is mostly 1st person POV of Bai Qian who is a very unreliable narrator bc she's full of shortsightedness and bias), and the boys love aspect (book: Qing Cang tried to marry 9, not adopt him; crown prince of west water king is gay; a lot of ppl thought mo yuan and ye hua are gay bc bai qian posed as a guy). The book actually had more info on bai qian' s other brothers than the drama.
I like the drama more than the book but some of the plot points in the book made more sense and allowed for more depths of character, even if those characters technically had less appearances in the book than drama (Qing Cang, for example). The order of the book is very interesting since we start with SuSu heaven trials then flashback to the KunLun storyline, but I think I like the ordering in the drama more. Additionally, I like how Ye Hua was portrayed in the drama more...Bai Qian is not very observant or insightful(but she's the narrator), so we don't get Ye Hua's emotional undertones and angst in the book...when we do get his perspective in the short stories additions, it felt a bit listy. Mark did a good job portraying Ye Hua (and Mo Yuan)...I felt for him more in the drama.
What both did well: zhe yan and bai zhen relationship...I am amused at the strong hints that was never truly confirmed...the book's hints were stronger but way to go drama for getting thru under the SARFT radar.