This Smashwords freebie (the full serial to date is also free on the author's site, it says) would be an Amazon 3.1, about 2.6 on Goodreads. It's not really quite my thing, story-wise, but it's far from the typical zombie tale. I read the whole thing "accidentally" via their online reader function when I'd intended just to decide whether it was worth downloading.
The story involves many casualties, including several failed "saves", numerous destructive action scenes, and (being a serial) ends on a fairly downbeat intermediate conclusion, with a number of elements not yet resolved.
The writing isn't bad, and though I didn't have the ability to mark errors, I don't recall many at all, but it's nothing special, style-wise. Not all of the scenes are told from Hector's PoV, and they're not labeled, so there's the occasional sentence or two of, "Wait, who are we now?" adjustment, but again, not that bad. Some of the wisecracks are pretty lame, as are some of the learning methods (e.g., crashing the motorcycle), and it's a bit odd that a being thousands of years old would sound so thoroughly modern.
Some gray areas are unexamined, e.g. re. Colt, and we've apparently barely gotten into the centuries-old conflict among reaper factions yet.
Also, though I'm not (for instance) an explosives expert, I wonder whether some of the things Hector does with his elemental iron abilities wouldn't actually cause more harm (shrapnel? suffocation?) than good.
Anyway, I didn't hate it, but although I felt bad for Hector's neglected and isolated youth, my curiosity about what will happen now is not enough for me to bother reading the next volume when I've got many better things in my Mount-Everest-sized (no, make that Olympus-Mons-sized) Kindle queue.