Mark Grayson is a son of a Superman (well, his father's last name is Grayson not Kent, his background story is different, and so is his costume, but he has exactly the same abilities - you know: if it walks like a duck and quacks like a duck...) He develops his super-abilities and starts fighting crime, this is all.
There is a foreword where they keep saying to the readers how the graphic novel is different from countless other generic superhero tales. Well, guess what? It IS a generic superhero tale. There is absolutely nothing new in here. A guy attends high school and tries to get a girl during the day and fights crime at night. I rarely see it in a superhero comic book, really: maybe in only 99% of them?
There is another huge problem I had with the novel. I always preferred Batman to Superman due to the simple fact that the latter is practically invulnerable which makes his heroics boring. The whole idea of Kryptonite came from the need to make him appear weak to something. This is exactly the case with Mark Grayson except that there is no Kryptonite for him: he is 100% invincible as the title suggests.
There were only two reasons I give an extra star to otherwise 2-star graphic novel. There are a lot of jokes in there. Some of them quite corny, but others are fairly good; the good ones are the first reason. Secondly, it is a very easy if mindless read. All in all, read the book if you already have it, but do not get out of your way to get it.
This review is a copy/paste of my BookLikes one: http://gene.booklikes.com/post/878834/a-completely-absolutely-undoubtedly-generic-superhero-story