This is an interesting game, but calling it a logical evolution of the 5E rules is a stretch. Any remnants of 5E are barely recognizable; that's not necessarily a bad thing as 5E isn't my personal cup of tea, but I think folks will be better off judging this product as a distinct new ruleset of its own rather than coming into it with preconceived notions based on their knowledge of 5E.
What's different about 5AE and 5E when it comes to rules? Just about everything - 5AE has no classes, no levels, a Death Funnel-style character creation system, an extremely lightweight character advancement system (even calling it a 'system' feels like an overstatement), no STR or CHA stats (replaced by EXP - Expertise, basically a weapon skill stat, and MAG - Magus, a stat tied to the new magic system), a different Alignment system, a completely different numeric scale for your stats, new races (called Genus here), a new combat system, a new freeform magic system, a talent system that feels kind of similar to Feats, changes to Advantage/Disavantage, and probably a few other things I missed.
Calling this an evolution of 5E rules is like calling Apocalypse World the logical evolution of 1st Edition D&D - true in the strictest technical sense in that 1E is the earliest common ancestor, but not a very useful comparison for someone interested in learning about Apocalypse World. That said, the 5AE rules are interesting and I'm excited to test them out at the table, the new magic system in particular.
Re: the setting/fluff, I enjoyed it a lot. Very cool world-building and unique concepts for a fantasy setting; if anything, THIS feels like where the 'evolution' occurred, as it feels like a 5E fantasy world that has (mostly) naturally evolved over a great span of time into it's current fantasy-futuristic state. The write-ups for the Genuses (Genusi?) are great and provide a lot of flavor to the world. The only minor quibble is that the writing style is a little inconsistent; in most places it's quite good, but in a few it scans a little weird, as if you're reading what was once a list of bullet points that was converted into paragraph form. Nothing that couldn't be fixed by another editing pass over the rough patches though.
Well worth a look, especially if you're aching for something different in a fantasy setting, just be sure to go into it ready to treat 5AE as its own game. 3.75 rounded up to 4, I'll update the score once I get some actual play under my belt.