Well, I've completed the manga and my thoughts are basically just uh wow, holy shit. That final gamble was one of the craziest things I have ever read. While I don't feel I should detail that specifically, it did make me think about a lot of things the manga did really well overall.
I've actually seen people say things like "the only thing Sako is good at is drawing close-ups", but I would argue, in a manga about mind games, being able to stylistically portray the facial expressions and body language of characters in a really interesting way is a pretty enormous strength. In this way games are often visually bombastic in a way that dwarfs the already impressive looking battles. The nature of gambles drifting between hope and despair is put on display expertly, which can make big moments feel both triumphant and stomach churning.
Personally, I think the writing is pretty great as well, even if its a bit uneven and convuluted in the beginning. Sako had to write this weekly for years, and still somehow managed to consistently set things up hundreds of chapters in advance. Building up Souchi as a character was a great move, as by the finale I couldn't imagine either he or Baku losing. As for the rest of the cast, well there's a lot of them, and despite a heavy-handed use of flashbacks I ultimately ended up really liking every single one. The unique personality of each gives different spins on all the events taking place, and its through their eyes that the reader can grasp what is happening. This also, conveniently, allows all the rules and conspiracies to be organically explained in such a way that even Marco can understand. Towards the end things get pretty experimental, and the manga starts playing mind games with the reader. There was one point where I legitimately got tricked and thought I accidentally skipped an entire volume.
I would not say the manga is deep, but there is definitely some pretty interesting ideas. One central theme is fate as determinism versus casualism. Souchi is "perfect". Through what can only be described as divine will, he is able to predict all that will happen with god-like accuracy and algorithmic proficiency, which leads to an outlook of determinism. On the opposite end, Baku is the "Fool archtype". Everything in life is a gamble, each passing second has an infinite amount of possible variations, and through self-determination he is able to manipulate the odds. As the two grapple they form a complicated yin and yang co-existance with an unexpected degree of philosophical complexity. Additionally, I feel the author has a pretty grim view of the world, and brings up some conspiracy theories I thought were quite amusing. Did you know the price of gun stocks often spikes upwards after a mass shooting? In a world where vice funds pay out high-quality dividends to such degree that one might consider it absolutely sinful, what does that mean for the people in power who hold the world in their palm? To give you an idea, there is a scene roughly in the middle of the manga where an arms dealer unceremoniously calls the entire nation of Japan unthinking cattle on national television, and mockingly tells them that despite being fortunate enough to live in a country where they won't even be shot down for flocking to the streets in protest they won't do anything. This is only a drop in the bucket really, lots of things to think about.
I really enjoyed this manga and would recommend it to anyone. One of the absolute best I have ever read.