The Dark Fantasy Basic Player's Guide offers a blend of old-school feel with mechanics that will look familiar to players of 5th Edition D&D. The overview on the product page as an old-school game with modern influences. I would actually turn this around and call it a modern game with old-school influences. That's not a bad thing, by any means, but the mechanics are closer to 5e than to B/X D&D, and I think that should be clear to any potential buyer. But that streamlined core doesn't have the same feel as the more heroic, high-magic standard that 5e offers by default. Instead, we have a very different feel here, which is much closer to many OSR and classic D&D games.
This game's introduction was particularly helpful. I appreciated that it offers some insight into the tone the designer is going for and the philosophy behind several game mechanics. This provides a clerer understanding of how the game is inended to be run and why the rules are what they are. I thought it was especially interesting that while the game is grittier and more dangerous than 5e D&D, this is somewhat offset by the default rule that PCs will start at 3rd level (with the option to start at 1st level). This helps with the conversion of old modules and OSR adventures into Dark Fantasy Basic, allowing levels to align, without having PCs die in a fight against a house cat (the example provided in the book).
The game is based on standard DCs that range from very easy (DC 5) to legendary (DC 30). When rolling to meet or exceed the DC of a challenge, you roll, add your attribute bonus (which is on an old-school scale) and your skill bonus. The skill bonus is similar to the proficiency bonus in 5e, but instead of either being "on" or "off," you either get the full bonus, 2/3 of the bonus, or 1/3 of the bonus, depending on if the skill is a primary, secondary, or tertiary skill. It's important to note that Combat is a skill, as is Spellcasting. Only the fighter can take Combat as a primary. Clerics and thieves take it as a secondary sckill, while magic-users take it as a tertiary skill.
Classes have the same XP and HP progression, which is another break from OSR games. There are no demihumans, which will lead to a different feel than the B/X games that are cited as the influence for this game. In the conversion notes at the end, there's a suggestion on how the special abilities of other races could be modeled using feats (see below), but no examples of what this would look like in practice. I would've appreciated seeing what dwarves, elves, and halflings might use as racial feats in the conversion notes.
Feats are more like class abilities than what we've come to call feats in most games. There are a handful of general feats that any class can select, but the rest are class-specific. This allows you to build a character who is mechanically different from other characters of the same class.
Hit points essentially have two pools, similar to vitality and wounds in d20 Modern. These are the character's hit points and constitution. The character isn't dead when their hit points reach zero, but they're at death's door, and are likely to still be on their feet fighting. However, if they take any additional damage, it comes off of their constitution, which leads to a fast death spiral. Natural healing is as slow as you would expect from an old-school game.
Alignment is on the Law-Chaos axis, with the option of being Unaligned, which is different from the balance-focused Neutral alignment.
The economy uses the silver standard. I couldn't get used to the dollar sign ($) used as short hand for prices in silver pieces. I had to remind myself that this should be "10 silver" when I read it in my head, rather than "10 dollars." It's a minor complaint, however.
Because PC death isn't uncommon in the game, there's a section dedicated to rules that cover new PCs inheriting both material and immaterial benefits from deceased PCs. This would remove at least some of the sting when you have to re-roll a character.
Spellcasting is based on spell power rather than Vancian spell slots. Characters can attempt to cast higher-level spells, but the DC goes up accordingly, and there are some dire consequences caused by spell mishaps. The Spell DC scale is different from the one used in the skill section, so you'll want to keep both handy during play.
Combat draws upon much of 5e's structure and language. Characters take an action including movement and a bonus action, and may take a reaction and one free action per round. Attacks can be made with advantage or disadvantage. Crits are possible on a natural 20 if it also exceeded the target by at least 5, or if you exceed the target roll by 10 or more, regardless of what's rolled. Fumbles are possible for other types of skills, but not for Combat, which is an interesting twist.
I often don't pay much attention to public domain art in RPGs, but the selections were particularly appropriate in this book. The author did a nice job of finding pieces that were thematically appropriate for the section they were included in. I should also take a moment to note the cover art, which I like. One nitpick, though: the cover and the piece on page 29 appear to suffer from what appears to be dithering. There are speckles or lines going through the gray portions of the art that don't look like they should be there. I doesn't take away from the product as a whole, but it would be nice to see an update with these images fixed.
There are a few formatting issues that I spotted. The Encounters section header on page 39 is written in a calligraphic font, but in all-caps, making it tough to read. The Athletics skill isn't bolded when defined on page 12. There are several examples where it's hard to spot a new paragraph, because the previous paragraph ended near the right margin for the column, and there's no indentation or additional spacing between paragraphs.
In summary, I like many of the ideas presented in this book. If you don't like how heroic characters are from the start in 5e D&D, and you want magic to offer more risk vs. rewards, but you enjoy modern D&D mechanics, Dark Fantasy Basic is worth checking out. There are more mechanics than B/X D&D or related retroclones, but if you like a bit more of your game codified, and you're seeking easy conversion between a moern game and old modules, this could be a great choice for you. There a few minor formatting issues I'd like to see fixed, and I would prefer to see demihumans offered as an option. However, this is nothing that a GM can't fix pretty easily.