My thoughts after reading it, in no particular order:
- Setting seems fine, nothing jumps out at me as a "wow super cool i have to play this" that i sometimes feel after reading a rulebook, but there is nothing bad about it.
- Basic mechanics need another pass. I think i understood most of the things, but even after reading it thrice im not super sure about everything. Maybe some things need to be explained in different order, or maybe examples are needed. Things like AP costs, and attribute actions i think i got, but i have the nagging feeling that it could work completely differently than i understood it.
- Everything needs a bit of polish, some sentences run too long, some explanations gloss over stuff that seems very important. Needs to be proofread by someone with little to no experience with the genre to see what needs more explanation.
- I would need to read a play by play of an example turn or even an entire combat before i would feel qualified to run the quickstart adventure. Something very simple like the hero vs 2 random thugs in an alley, it should be enough that every mechanic could be used once before the fight is over.
- Heat sounds very cool, simple risk-reward systems are my jam, and degrees of success is something i always do in my games, no matter the system, so i like it's baked in. Reflex is iffy because it relies purely on luck, i just see my buddy making a reflex based ronin and just never rolling doubles and being stuck with basic attacks.
- As for the adventure, its fairly non-linear, and i can see the player doing some stuff that will leave them with no further clues or skip half the drama.
I do love non-linear stories, especially whodunnits with multiple plots at once, but it does feel like a bit much for a testrun adventure. If i had to juggle a new ruleset on top of the adventure, i would for sure mess it up. I do like the story and i wouldn't want to simplify it, but i feel like it needs a little rewording to make it flow more intuitively. Maybe the adventure could have some sort of a checklist, a glossary or even a flowchart. Or a cool map of all the areas and what happens in them?

I geniunely dont see how this can be an alternative to SR when it lacks the components that make Shadowrun "Shadowrun"
This is fine as a simple Cyberpunk game, but it wont be an alternative to Shadowrun in any fashion.

While the idea of success increments is fairly intriguing and the heat system is genuinely good, this book largely falls flat. The prose is more than a little weird, which makes it feel stilted to read (Most especially in the opening lore bit, which feels like something from you'd read under an early Deviantart upload). Especially the Hook line at the end of the opening
"Oh... and don’t piss off the wrong people and don’t get yourself killed!"

Actually made me cringe to myself.

Other than prose, there's weird grammatical issues and a limited vocabulary that make it awkward to read and give the impression it never received a second pass. Such as using "but" in the same sentence twice on page 12, made worse because this is a section the GM is supposedly expected to read out to the players. I call this out as an example, but note there's usually one such mistake per page. For example on Page 4 "Each of them has their stat that exists to increase the damage of your attack when using that type." is just a really awkward sentence.

I really recommend, before you take this any further than a proof of concept, you have someone else read through your quickstart rules. Even just reading it to yourself, out loud, will probably help you identify the readability issues that plague it. Overall, this feels like a Microsoft Word document thrown together over night to play at home and not something you expect to show to people as a genuine game.

The adventure that comes with it is rather milquetoast and I doubt it would hook anyone in to long term play. 

Outside of the poor readability I think your attributes, skills, and stats need another pass. The system isn't well explained, and if I understand it correctly not all of the sample characters fit the system as described. Such as the Ex-Detective's strength not justifying with his skills.

For a positive, I like the heat system. It reminds me of Momentum in Star Trek Adventures, which is genuinely the best part of that game. However, Reflex feels like the kind of thing that would just frustrate players quickly. I think the Reflex Points would be houseruled before the very first game at my table. So give and take I guess.

I may seem harsh, but you're presenting this as an alternative to Shadowrun of which the primary complaint is often it's poor editing and flow. If you want to compete with them, you need to at least as good as them in that department.