Plot/Story
A regular sports story with a typical plot, but Eyeshield 21 has its bright sides. Sena Kobayakawa is a small, cowardly boy who has just entered high school. He had been running away from and serving bullies all his life, and always seeks protection from Mamori Anezaki, his childhood friend. Hiruma Yoruichi, captain of the Deimon Football Team, sees Sena's fast and amazing running and forces Sena into the football team. Along with the football team is Kurita Ryoukan, who has dreams with Hiruma to go to the Christmas Bowl. Soon later, Mamori decides to become secretary to help out Sena, who is concealed as Eyeshield 21 to let his identity hidden. Sena is motivated to keep playing football after seeing an amazing rival, Shin. They later on gain more teammates and formulate more techniques.

The story is cliche in the way that everything goes in tournament style, they name their "techniques," the main characters have their motivations and some with dark pasts, and how the main character has his "extremely-beat-up-but-determined" moments. However, there were good aspects too -I liked how there were no impossible "power-ups" like there was in Prince of Tennis, and how it showed a lot of the training (like they did in America). There were good and bad aspects, but the typicality of it all was the biggest "bad" factor.
Characters
Sena - A wimpy, weak highschooler who has amazing running abilities from years of dodging and being an errand boy. His codename is "Eyeshield 21" to hide his identity and to keep other teams from trying to recruit him, and in the football field he uses an eyeshield and wears a jersey with the number 21. His goal is to defeat Shin, of the Oujou Knights Football Team.

Mamori - A caring girl who watches out for Sena. She has always been watching his back, and the reason why she became secretary was because of Sena. She is oblivious to the fact that Sena is Eyeshield 21, mainly from the fact that she cannot imagine him being a football hero.

Hiruma - The captain, quarterback, and founder of the Deimon Football Team. He keeps a book with embarassing facts about people that he can blackmail with. He has regular statistics but he is the brains of the football team and decides what to do.

Kurita - A fat, big, food-loving lineman. He's a giant, but he's very friendly and polite. He was also with Hiruma at the start of the club and has dreams of going to the Christmas Bowl. He's a bit of a crybaby at times, though.

Raimon Tarou - Also known as Monta, this monkey look alike originally had dreams of being a catching hero in baseball like his idol, Honjou Masaru. Ever since Honjou had given him his broken baseball glove, Raimon wanted to be just like him. However, the only good aspect of him is his great catching, but his throwing abilities are atrocious, so his baseball is not recognized. He joined the football team to be the catcher because unlike baseball, football needed people with specialities.

Ichimaru Tetsuo - A guy from the track team that always appears. He's very nice but is a big pushover. He keeps on playing for the football team although he has no significant abilities -he's just really there to fill in the empty spots.

Juumonji, Kuroki, and Toganou - Named the "huh huh bros." They are all linemen and have been called trash many times, and were originally bullies of Sena. Juumonji seems to be the only smart person of the trio, and is pressured by many people calling his friends trash. Although they only really joined the football team because of Hiruma's blackmail, they get serious about it later on.

Yukimitsu - Your average studyholic nerd. He's been attending cram school for quite a while, and his mother forbids him to do any extra curricular activities. However, he decides to join the football team because of his desire to do something other than studying. His idol is Eyeshield 21. He is weak and has less than average abilities.

Komusubi Daikichi - A lineman. His idol is Kurita, and decides to be his apprentice. He's very short, which gives him struggles, but also very strong and determined. He hardly speaks and when he does, only powerful people understand him.

Shin - Part of the Oujou Knights football team, he is their ace. He had been the fastest high schooler until Eyeshield 21 came into the picture. He is very strong though not insanely tall. Not much is known about his throwing and catching abilities (probably average). He is very bad with technology.

There are a lot more characters and somehow we all get to know them, and the best way to know them all is to read the manga. They're actually pretty deep but it annoys me that each has some dark past (or their past is exaggerated).
Drawing Style
Nothing amazing, but the artist is able to portray football quite clearly.It won't get anyone to read it just for the art, or to not read it because of the art.
Enjoyment
It depends -if you like these kinds of shounen it will definitely do its job, but if you're just into the manga and not the sport or into tournaments the enjoyment level might go down a little.
Overall
I suggest people to try it out. Although it's not completely original, the manga has good aspects and some people tend to love it, even though others stay away. Overall, a good read to pass time or from boredom, but nothing to stay up until 3 AM to read.