The Double is a drama adapted from the book, Marriage of the Di Daughter, which I read last year. I binged on the first 5 episodes last night when it was released because I loved the book so much. So far, the drama has exceeded my expectation in everything except:

The modification of the story makes it hard to believe that she could take on the identity of the new daughter ... There are a few plot holes resulting from this change. I think I am going to just have to ignore the nagging "doesn't make sense" feeling because the drama is entertaining. Sometimes you just watch because it's entertaining.
Book: "Xue Fang Fei, passed away. She reincarnated into the body of the Grand Secretariat’s daughter, Jiang Li, who drowned and was granted new life!"
Screen play: "Xue Fang Fei escaped from being buried alive by husband and took over the identity of Jiang Li"

Ok now that the book expectation is out of the way, I believe the screenplay modification is more entertaining than reading the book. I will continue to watch because:
1) the solid acting from all the casts:

Wang Xing Yue has great screen presence. He is perfect for this role ranging from his deep voice to his looks/costumes. I just wish that there isn't too many jokes around him because I think it would diminish his characterization.

Wu Jin Yan also acted well ... revenge is her territory since the drama that made her famous- Yanxi Palace- I am waiting to see how she will make this drama her own.
Let's address the elephant in the room: agism for females as well as males. Wu Jin Yan is 33: to act like an 18-9 years old is hard, especially when all the actresses around her look like teenagers or 20s. No amount of filters can make her look like 18 years old because aging is about facial structure, not lines. In the 20s, the face is fuller, especially in the cheeks. And to make it worse, both MLs are only 22. She has a tough job ahead of her.
If you place 2 people who are similar age, then it's easier for the actor/actress. But the cast includes really young actors: her maid is only 15! The MLs are both 22. Appearance of age is all relative. That being said, if the story is engaging and the Male Lead is a good actor, chemistry will do the work.

***
For people who are concerned about an older actress - by episode 20s, I don't notice it as much any more. I think there's enough chemistry between the leads and good story that overcame the age factor.
***

Joe Chen - the stepmother added subtle acting to this drama - she is the stepmother coming alive.

2) the beautiful cinematography - the color palette, makeup, costumes
3) the entertaining value - fast-paced action, music, comedic value

Do I recommend this drama? Yes, especially if you are fan of Wang Xing Yue and Wu Jin Yan. The story is also solid. Although I have read the book, I feel that there may be surprises as they have changed it.

---------------My Rating Changed
Ep 11 is where I decided to give this drama a full mark instead of a 9. I think the creativity of last competition is very well done. The special effect is spectacular! And I also feel that the age difference between the leads/the plot holes are minor compared to all the positive things going for this drama. I also feel that Wang Xing Yue, even though looking younger, does have chemistry with WJY.
Surprisingly, the actor for Ye Shijie is also decent. He looks mature for his age too.

------------------Douban rating explained
The Double got its initial Douban rating of 6.9 ... I don't take this rating seriously because it's skewed towards dramas that I don't like :-) Just for comparisons, Love Like the Galaxy, which is my all time favorite, debuted at 7.4 and ended at 7.6! I think it should have been in 9s!!! But then my taste is more geared towards romantic dramas and better aligned with mydramlist rating.
Anyways, ratings between 6s to 8s are really good dramas for me ... anything from 8s to 9s are usually too serious/realistic (i.e. sad realistic endings) for me enjoy. For example, Blossoms Shanghai rated 8.4 ... Honestly, I don't enjoy this type of drama.

------ Exceptional Scene
Ep 16
The actor who really fits the role in this drama in looks and as well as acting is Wang Xing Yue. Wow the fighting scene at 14:32 ... His eyes really give the deadly chill. The director filmed the fighting scenes perfectly. Very exciting fights.

------- Love story/Relationships - believable?
To be honest, the book is more believable than the drama because in the book, she becomes another person, Jiang Li. It took her a long time to accept new love. In a way, I feel that living in another person's body is easier than the living in a body that has been abused. When I read the book, I felt that the purity of JL's body and innocent face/eyes also help transform her and help her find love again.

Some people said that her relationship with the Duke is so slow ... Come on, she was in love with her ex-husband before he betrayed her. Feelings/trust cannot be switched to another person that quickly. It wouldn't be believable. I find the change in her demeanor (ie. flirting) in the drama (while creating chemistry and entertaining) is not realistic for that time period during which a woman behaves more modestly.

But again, sometimes you just have to let go just enjoy the ride without thinking too much about what makes sense.

-----------------Modifications of the book
In the drama, JLi doesn't know that the princess is behind her death. While this doesn't make sense as her ex-husband goes to the Princess' home often and there's probably rumors about this. However, this makes sense for the plot line because it gives JLi a mystery to solve.

Ep 8-11: In the book, JLi is a only person doing all the examination topics: "Jiang Li calculated, calligraphy should be writing documents. It’s something that she was good at since young. Music should be playing the guqin. In her previous life, her seven notes qin was about the same as Xiao Deyin, so it’s not too difficult. Etiquette would be even simpler with her outstanding memory. Besides, she had gone through it before. Mathematics should be business calculations. There was no female in the house since she was young so she was the housekeeper and managed the household. Riding would be horse riding, she had also practiced this with Xue Zhao before and was applauded. Shooting would be archery, she had gone hunting, shot a sparrow and ate game."
However, in the drama, there is a teamwork in the examination. This makes the story more interesting.

Ep 11
In the book, Duke Su makes the winner decision instead of the ex-husband. I just feel that changing the plot to make the husband into a semi-good character is a little bit hard to accept.

------------------ Where's the First Miss? --------------------
There 3 daughters in the Ji's family. The first miss died when she was young, killed by Ji Shuran, whose goal was to get her offsprings to be the only direct descendants. So one by one, she removed them.

------------------- Explanations / book exerpts
Jiang Li's family background from the book
https://bloomingtranslation.home.blog/2019/09/01/mdd-chapter-2-1-jiang-li/

Ji Shuran - 2nd wife- the current "official" wife.
Jiang You Yao - 3rd daughter - Ji Shuran’s biological daughter- became official daughter when the 2nd daughter ( Jiang Li) was sent away
Jiang Li - Jiang family’s second young miss- sent off to the temple to study due to a mistake she made five years ago (accused of causing stepmom's miscarriage),

https://bloomingtranslation.home.blog/2020/11/01/mdd-chapter-39-part-2/
Jiang Yuan Bai - Jiang Li's father- married her mom without love. When she died, he fell in love with Ji Shuran and married her.

------------- Excerpts from the book - description of Jiang li
"Everyone said that the second miss of the Jiang family was lively and adorable, with an honest character as pure as a white lotus."
"Jiang Yuanbai looked at Jiang Li’s profile, an elegant beauty, graceful like jade, yet ferocious, bold and heroic."
" This girl’s eyes were pure and clean like pools of spring water, sweet and simple."