Ah yes, a manga I stumbled upon years ago. Heavily disappointing as my first review on here...
Doll's code at first glance of the synopsis and peaks is an interesting manga and not for the easy faint of heart due to some of its subject matters it fails to do mostly anything about if it's not murder to say at the least.
[story: 6/10]
With a basic yet still boring plot forcing them to "bond" to understand each, and you know, get your body parts back from Frankenstein .JR.
The mystery is interesting having most viewers on their feet, even keeping the identity of the puppet for most readers or those who don't put too much thought of it hidden well for most and obvious for some others.
However, this is where its problems arise. They have it too mysterious without pushing us in the right direction. Oku always gets the finger pointed at him as the puppet. It's like they never give you a chance to say think "[name] might be the puppet!" Making those in the manga suspicious of Oku with no reason/ Literally one chapter they don't trust him, the next they do, after that they don't again, and repeat! It Results in making the "bonding experience" of the characters useless and pointless to show these sides of characters if it's not the twins.
In most parts of the manga I never got the slightest bit disturbed at scenes.  The only time I felt frightened was through two backstories, and only because to the sudden graphic content without saying "Hey here's backstory, LOL!"
[characters: 3/10]
Easily forgettable and almost useless outside the "actual main two" and three others. Featuring awful backstories for everyone but one. This made minor character development hard to create with the exception of one, and even then it's for the most "complex" of the bunch. While he's the worse compared to the rest of the cast for a variety of reasons, I don't know how I can explain how stupid that was without risking spoilers.
[Art: 9/10] [Enjoyment: 5/10]
Probably for most the only charm point of this of course is that beautiful art and character design! I only found myself continuing to read it just to see more of the style, being as that's where I found most of the "enjoyment" (if I can really call it that) from.

TL;DR: dolls code is just boring with typical trope characters you'd find in most early shounen animes but trying to be dark and gritty like watered down dangan ronpa and sucks at trying to make you feel sympathy for characters.
However, Dolls Code is worth enough a skim in your spare time or a quick midnight peak if you want a chapter or two. In all honesty too; you could stop reading this for a year and suddenly remember and go straight back to where you were since you're not really forgetting or missing much, lets be honest here.