I really enjoy this Halo fanfic. It's the only fanfic I read, and I've been reading it since I stumbled across it.
The story revolves around Francisco Castillo, known as Frank, and his time in the UNSC. Almost all of the story is told from his point of view, in first person. I am not the most knowledgeable person when it comes to Halo lore, but at the very least the story is internally consistent.
The main problem with The Life is the writing. English does not appear to be the author's first language and in the earlier chapters, there are many errors in spelling, grammar, and word usage. After a few dozen chapters (there are 194 as I write this), the author makes use of different proof-readers and quality increases. After so many chapters, author's knowledge and usage of the English language has greatly improved and there are few errors.
The focus of the story, as I already said, is Frank, who is quite the badass and pulls off a number of remarkable escapades, first solo or with his partner Pavel (the supporting cast plays a much more minor role in the beginning of the story) and later in the story the escapades often involve multiple soldiers in Frank's team and other soldiers. This has resulted in much longer battles.
The story has a lot of action. I find it not to be a heavy read and while knowledge of the Halo world helps, even just having played a game or two in the series is enough to understand the overarching idea of the Human Covenant War. The recurring cast of characters are fairly well developed, but are simple enough to just read a couple chapters a week and retain an understanding of the character. I enjoy all the characters, even the ones I hate.
As a cautionary note, there is strong language, alcohol use, lots of violence, and suggestive themes. Basically it fits the T rating it has.