Having read/watched an ungodly amount of stories, this is the greatest thing I have ever experienced in my entire life. I read the visual novels first, which I highly recommend for you to do so because this story is based on a visual sound novel that put in a significant amount of effort in creating an atmosphere with sound effects and the most amazing sound tracks I've ever heard for background music. The only thing lacking from the sound novels are the beautiful artwork present in the manga.
Umineko no Naku Koro ni, or When The Seagulls Cry, is an extremely long novel revolving around the events on Rokkenjima on October 4th through 5th in 1986. There is a large cast of characters full of personality, and the depictions portrayed throughout the story are believable that something like this could actually happen. The Ushiromiya family is a rich and powerful family thanks to the family head, Kinzo, who is said to have received ten tons of gold from a deal he made with a witch just after World War II. The whereabouts of the gold is unknown, or even if the gold exists at all. An epitaph is constructed in the mansion in front of a portrait of the witch, to which whoever can solve this epitaph will receive all the gold and become the next family head. In his old age, Kinzo has gone senile and dabbles deeply in the occult as he attempts to revive the witch, and does not have much time left to live. Due to a typhoon, the family and servants are trapped on the island for two days during their family conference, or squabble, over the inheritance. As the family and servants begin dropping one by one with seemingly impossible murders, by the time the seagulls cry, none shall be left alive.
I will present to you readers some hints as to what you should look for so you don't stray from the path. Many people get into this story only to become confused for their lack of intelligence and understanding of the material. There may potentially be a few minor spoilers, but they won't detract from your experience.
Like Higurashi, each episode here is an alternate world, a fragment, of what could have happened. Hidden within each fragment is the truth, with the culprit being the same for all fragments. Rokkenjima of October 4-5 in 1986 is a catbox. If you open the catbox, there can only be one true outcome. If you keep it closed, there are many possible truths. The story will end without opening the catbox completely yet arrive at a highly satisfactory outcome. For those looking to discover the truth, the clues are all provided throughout the story to piece together your own truth of what happened.
This story is more than just a single story. There is a story hidden within the story hidden within the story all playing at the same time. Ushiromiya Battler is our detective on the island of Rokkenjima. His perspective is that of the objective perspective, and therefore can be taken as reality; unless we are to believe that Battler is the culprit and his perspective is not reliable. Any scene not seen by him is the subjective perspective which may or may not have happened. The magical perspective also lies within the subjective perspective. Another perspective is the perspective of the metaworld, revealed to us at the end of episode one.
A game is pieced together starting in episode two as a crutch to help you think. This is the game of Blue Truth versus Red Truth. A battle of intellectual wits against the idea that magic is not real and the witch is a delusion, all crimes were committed by human hands. The Red Truth is the power the witch will use against Battler. The Red Truth is the absolute, undeniable truth. However, the red truth can be misleading as there may be multiple interpretations of this red truth. The goal of Blue Truth, similar to theories, must present a truth that does not violate the Red. If you can create a truth for this story that doesn't violate any of the Red truths presented in the story, then you have arrived at a truth for what happened, who did it, and why they did it.
The metaworld is an unknown realm existing alongside Rokkenjima; it cannot be proved nor disproved. Whether it is purgatory or some realm on a higher plane does not matter. To the characters here, Rokkenjima is like a chess board; they do not have anything directly to do with the events of Rokkenjima. The Battler presented here is not the same Battler you see on Rokkenjima. He is, at best, Battler from the first episode looking over the events of other fragments trying to piece together what happened.