This quadrilogy is mind-blowing. I just finished the third installment and heck, I suggest reading the first two just so you can read the third. The writing style and characterizations get better with each arc, so even if you aren't blown away with the first, I still recommend continuing. The third chapter was so incredibly beautiful that I am ready to start from the beginning and read it all over again-- and I don't usually have the attention span or dedication to long fanfic.
[This is copy/pasted from my rec post.]
- Out of the Nest is the only continuation fic worth recommending. It's believable and much less contrived than others. It's very in-character (though they left me a bit chilly somehow, despite that) and takes vaguely suggested plot points from the series and turned them into the focus of the story. Give it a shot.
- Loss of Life, the sequel to Out of the Nest. His writing style has matured since OotN and the characters feel much warmer. This has a lot of focus on Moondoggie as well as Renton and Eureka's purpose in this new world. The ending scene is an awesome punch, as well.
- And I Shall Be Your Light is the BEST of this quadrilogy so far. Eureka is painted so incredibly wonderfully in this installment and the importance and deep relevance of hers and Renton's relationship to the new world really comes into play. This is an absolutely beautiful installment; read the previous two just so that you can read this.
Hope someone else loves them as much as I do. It's the best lengthy E7 fanfic out there. Enjoy! :D