In my opinion, there are two parts to Gamaran; there's the intense and fast-paced action up to around chapter 60 and there's... the rest.

- - - S T O R Y - - -
The story is pretty weak, to be honest. In fact, up to around chapter 60, there's barely a story at all. It's pretty much just all about Gama wanting to get stronger. The manga is amazing action at every turn. Each enemy is a master of a different martial art, most of which using different weapons, which keeps things really fresh and interesting. Things go from one battle to another immediately before the main characters have a chance to rest, then they continue the battles even while they're resting. It's pretty addictive to read with how the action doesn't let up. It's also great how the enemies are killed in just about every battle, so you don't get predictable repeat battles and drawn out crap. The technical explanations and the way every match has everything on the line makes it quite enjoyable. The intensity of the matches is similar to Hajime no Ippo, but with no training scenes or personal life.

For "the rest", the story develops a lot more, but the action dwindles. Whatever foes weren't eliminated before have their roles dragged on till the later chapters of the manga. For some reason, the author also decides to start giving nameless characters backstories before they die. To make things worse, the battles become a lot less realistic, less focused on weapon variety, and they last longer.
The later enemies are far too gimmicky and can barely be called martial artists. That's always the worst part of shounen manga in my opinion. DBZ went from martial arts to shooting beams at each other, Bleach went from samurai action to shooting beams and clashing swords while never actually cutting each other, Berserk went from medieval wars to solely fighting monsters. The enemies in Gamaran are still human (mostly) and they still get cut and die from mortal wounds, but it's just not the same, and just not as good. Thankfully, Gamaran never resorts to a "power level" system where the battle is over before it starts, like in Toriko or the later YuYu Hakusho.

- - - A R T - - -
I dunno why the other reviews are hating on the art. I thought the art was well done. It does have some similarities to a cross between Naruto and Bleach; that is to say the art is more realistic than typical anime/manga, but still keeps the part of it that makes it appealing.

Characters have the different kinda faces you'd expect from manga. That is, you're bound to come across some pretty familiar faces as far as eyes, noses, head shapes, and hairstyles go. Some of the characters have pretty distinctly different eyebrows, though, which I think helped with making them look different.

I think the setting is quite well done. Pretty much everyone wears things like hakama and kimono. This manga doesn't have the "badass" samurai who walk around shirtless, carrying 9 swords, wearing bright red clothes and armour, etc. (I'm looking at you, Sengoku Basara). There is a lot more discipline and respect for the blade in this manga, and the way everyone dresses in traditional clothes makes it all the more convincing.

The colour pages disappointed me, however. For example, Zenmaru's hair is red. Why would a Japanese person in feudal times have red hair? There are a lot of characters with white hair, which, in manga, means it can pretty much be any colour. This part really doesn't fit in with the setting. There are some characters who are introduced as foreigners and they have blonde hair, which is fine, but what's everyone else's excuse?

- - - C H A R A C T E R S - - -
I have a few complaints here. Let's see...
Hyuga Bros.: They join the Ogame school as comic relief characters. They wish to learn the Ogame style, but are essentially ignored. I think they could've developed into cool and respectable characters given the opportunity. Obviously, they shouldn't be as strong as the main characters, but it'd be nice if they were able to at least offer some support.

Iori: He was incredibly badass. He always looked like he had such intensity to him. After a certain plot point, however, he becomes incredibly tame. Even the way he's drawn, his eyes just don't look as crazy as they used to. He's barely present in the story, so... come on, give us the true Iori when he's actually there, not this watered down version. The author probably wanted to give him rivals, but toning down Iori is not the right way to do it.

Ogame girl: I don't remember her name. She pretty much had no reason for existing other than offering some rare opportunities for jokes, which weren't even funny. It would've been cooler if she secretly knew how to fight.

Naoyoshi: Based on the relationship between his mother and Jinsuke, I thought he surely had to be Gama's brother, but nothing about that was ever elaborated on. It just kinda feels like a disappointing loose end.

- - - E N J O Y M E N T - - -
The humour in Gamaran is pretty weak. They shouldn't have even tried. You can only comment on Gama's lack of pubic hair so many times before it causes your humour senses to cry instead of laugh. What are we, 11 year olds? Kashitarou's obscene fantasies also weren't funny.

I'm glad this didn't have some ditzy, big breasted character, though. In fact, it barely had any females at all, which was surely for the best. Fan service is one of the worst parts of the industry.

I also feel I should mention the story has plot twists during "the rest", and you might not always see them coming, but, to put it bluntly, they aren't exciting.

- - - O V E R A L L - - -
Overall, this was pretty cool. The first 60 chapters were exceptional; perhaps the best battle manga I've ever read (and better than battle anime I've seen). It was all battles with no bullshit. Plus the battles were actually cool and had depth to them, not just senseless violence like Hellsing.

I recommend reading this up to the point where Ranmaru captures a certain person. Things go downhill after that, though. Before that is 9/10, after that is 6/10.

PS: The ending is pretty anti-climactic.