So, here's the thing with Liar Game.
The second half is straight up dog shit. It's a truly classic example of an author apparently improvising a narrative and chopping off an end to order, like a drunken butcher. The first few arcs are tremendous, speaking to an enormous conspiracy and promising incredible escalation. Our wimpy protagonist and her invincible sidekick have good chemistry, and bit by bit she hardens without compromising her principles. Game by game, the series steps it up, becoming ever more phenomenally tense, paranoid, complex, exciting and weird. It's a fantastic run while it lasts.
But it suddenly starts coasting. Then it stalls. I think it happens around the second Yokoya arc. In his first game - the clever little bastard, Yokoya, is a legendary presence, a terrifying enemy and manufacturer of truly frightening machinations. His Orwellian grip on his group and their secret rebellion against him are some of the most gripping, even slightly surreal, psychological drama manga I've read to date. When the cast's efforts to take him down finally pay off, it's a guaranteed breath of relief. Best of all, when he resentfully ruins the moment, our hero Nao - who seemed like such a crybaby - very politely argues him down and utterly demolishes his sore loser's pride, saving the day where the resident genius could not. It's a wonderful moment of character development for her to honestly, conclusively best such a powerful foe.
Then Yokoya turns into a joke. He pulls a Vegeta and keeps coming back, unconvincingly vowing I'll get you next time!! In the next arc he can barely rebuild a gang; he gets clowned around and literally bowled over and knocked on his ass. Why's he still here? He's not charismatic or smart enough to be Akiyama's rival anymore. When his mask is off, he's just an annoying little rich kid with several complexes. What an awful antagonist! And it really obviates Nao's success, if he's not really defeated - worse than that, if he's never going to be concretely defeated. There's no point to fighting him if he's just going to come back with new toys like Wile E Coyote.
From there on, if I recall correctly, things just go down the toilet. There's no advancement, just increasingly arcane and stupid rulesets that feel like "Takeshi's Castle" rejects. Akiyama and Nao, the most important characters in the plot, are allowed to go stale like unattended croissants. Then, to really pull the chain, Fukunaga, the bright star in the cast, gets unceremoniously written out entirely! Why would you do that to the most inventive and unpredictable character?!
Of course, like many others have said, the ending is trite and unexciting. "Everything is exactly what it looks like, the end." In fact it has the same "powerful men behind the government conspire to harden up the country" conceit as Kongou Banchou, a fighting comic for ten-year-olds, but Kongou Banchou made it artful and elegant and fun. The sad part is that even though the ending comes out of nowhere, I was begging for it to happen.
But I still recommend it, at least for the first couple arcs! You'll know quickly whether or not the series is for you. The things the series does right are absolutely stunning. Every rule is bent and exploited, every detail is important, and each arc has a ton of effort put into it. The character art uses formal realistic proportions and makes everyone easily distinguishable.
Not only is Liar Game gripping and likable, it's highly approachable. This is a comic of endless, wall to wall insanity and unforeseeable twists. I say, if you're a fan of "formal mindgames", like the stuff you see in Death Note and Kaiji, you really owe it to yourself to read this today.