Story: Liar Game starts off with a simple enough concept. A girl gets a package in the mail from the "Liar Game Corporation" full of 100 million yen, and finds out that she is playing against her old teacher. At the end of the month they each have to pay 100 million yen back to the LGT... but the catch is, if you can steal the other person's 100 million yen, then you get to keep the extra and the other person gets put into debt that they can't possibly ever pay back.
So the girl, Nao Kanzaki, gets easily tricked by her old teacher and enlists the help of a mysterious dude named Shinichi Akiyama. From there the two of them progress through multiple rounds of the Liar Game, each round different and more difficult than the last. The winners of the higher rounds win more money than they could have won from previous rounds, but the losers are entered into even more debt.
Art: The art style is nothing notable. It gets the point across in a clean way, but backgrounds tend to be pretty secondary. There are a lot of scenes that just focus on people's facial expressions where the background is greyed out, and the character designs aren't exceptionally note-worthy, aside from the huge range of character designs the manga employs. In many manga, each girl looks indistinguishable from the others save for the hairstyles. However in the Liar Game, it is often easy enough to spot the more frequented characters just by looking at their eyes alone.
Characters: You don't see the main characters outside of the Liar Game often, unless it is mentioning the few days leading up to the new round, anyways. Backstory is sometimes revealed and there is loads of development, showing easily how some people become less selfless or how someone who was an enemy at the start eventually becomes a loyal ally.
Most notable is watching Nao Kanzaki get tougher and (somewhat) smarter through Akiyama's coaching.
Overall: Overall the manga is very interesting, if you like heavily psychological manga. It has a lot of text but the games are so suspenseful with loads of dramatic twists and turns that make it a worthwhile read. For some point of reference, think of the really talkative episodes of Death Note and remove all of the supernatural-ness.