Land of the Lustrous (Houseki no Kuni) is an Action/Psychological/Mystery manga written and illustrated by Haruko Ichikawa. It started in 2012 and is publishing in Kodansha's Monthly Afternoon magazine. The manga currently has 11 volumes and 95 chapters.
The story is set in a distant future in a world inhabited by "gem people". They all live their lives together along with a sensei. The gem people are often under attack by Lunarians, mysterious creatures which come from the moon and attack for unknown reasons. The gems fight the Lunarians every day, and sometimes suffer great losses when the Lunarians capture them. For this reason, the gems are constantly trying to find a way to bring their people back from the Moon and uncover the mystery of the Lunarians.
Although the concept of a civilization being under attack by mysterious creatures has been done many times before (like Attack on Titan), no manga executes it as well as HnK. The story is unpredictable and full of surprises, always making you want to continue reading to find out what happens next. The story is very exciting and moves at a quick pace.
Aside from the very intriguing story, the part where HnK shines is its characters. Each of the gems are based on.. well... real gems, and each of them has their own unique designs and personalities. The main character, Phosphophyllite (picture below on the left) is one of the best written characters I've seen and has amazing character development. At the beginning of the series they (the gems don't have a specified gender) are a cute and bright individual, trying their best to get the other gems and the sensei to like them. As the story progresses, they have several traumatic experiences, which gradually change their personality and worsen their mental state. One such example is after the Winter arc after which Phos is no longer a cute character who can't manage to fight, but much more serious and one of the main fighters. Throughout the manga, they try to uncover the secrets of the Lunarians, and even the secrets of their own sensei. Apart from mental development, Phos has a ton of physical development, for example: getting different legs, changing height, getting arms of gold alloy, and at one point even getting a different head.
The side characters also have their own character arcs and problems they have to deal with. Some examples are:
Diamond, who throughout the series wants to do things on their own and separate from their partner, Bort.
Cinnabar (picture below on the right), who due to a venom which emanates from their body, is always away from the other gems and wants to feel somehow more involved with them.
The art style of HnK is very unique but simple. As said before, each of the characters has their own designs that make them different, and their hair is the color of the real life gem. The art isn't particularly fascinating all the time, and certain things like the shading and lighting don't really stand out. Despite this, the manga still manages to have amazing panels in the later chapters that stand out. One example is below, but be wary of massive spoilers.
Spoiler, click to view
A lot has already been mentioned about the amazingly written characters and story so I'll just say some smaller things.
The manga has great dialogue ranging from funny and comedic moments to dramatic and philosophical moments.
Some notable quotes:
“Power always comes with a measure of loneliness”
“Being clever sometimes makes it impossible to take action.”
“To come to acceptance with things and feelings is rare and to accept them completely is a miracle. It's impossible to make that moment come faster by yourself. Someday it comes unexpectedly. In order to not become warped or heartless, let it go in a natural way. Let yourself feel sad when you are, and let yourself forget when you do.”
In my opinion, Land of the Lustrous is a must read manga if you enjoy things that focus on the story and characters, with great action moments and well written dialogue. If you are a fan of manga such as Attack on Titan and you want sometimes infinitely better, then check HnK out. I promise you won't be disappointed.