Hags are among my favorite D&D monster, and one that is criminally underutilized in official material. Though always evil, they can be extremely versatile from a storytelling perspective and are great if you want to inject a bit of dark fairytale creepiness to your campaign. With that said, let's have a brief overview of what this supplement brings to the table.
Elder Hags, for when you want to make your crones especially powerful. The official material has made mention of Auntie and Grandmother hags several times, but there are no official rules for creating these ancient witches. This part of the supplement scratches that itch by providing a list of new features that apply to all elder hags, as well as a unique ability for each type of elder hag, such as the Annis Hag being able to create a small earthquake that knocks nearby creatures prone or the Sea Hag releasing a burst of horrific odor that poisons nearby enemies. There's also a short description of two sample Elder hags, an Annis and a Sea Hag, each of which could easily be slotted into a campaign.
19 hag-themed magic items and 110 "weird magic" items, including a rusted knife that fills children with murderous intent and a rattle made of a child's bones that incapacitates enemies with laughter. Perfect if you want to add a some macabre unique loot to a hag encounter, or to give to a hag to make them a bit more powerful. Many can also be easily repurposed for a wide variety of evil characters, and would be great for the party if they're playing an evil campaign.
Hag Weaknesses is a small section that provides examples of some of the esoteric weaknesses that hags might have. Could also be used for basically any fey, since most of them are taken from folklore of fey weaknesses.
Non-Evil Hags is a section that explains how a DM might want to play a non-evil hag. Personally I'm not a big fan of the idea of a good-aligned hag, since they always seemed like magical creatures that are just sort of inherently evil in the same way that devils are. Though neutral hags seem more plausible to me (and frankly more interesting than good ones). There's also short descriptions for five sample non-evil hags, (three good and two neutral) that could be incorporated into a campaign fairly easily, or act as inspiration. One of the sample hags in particular, a True Neutral Night Hag working to undermine a demonic cult whose master she has a grude against, could act as a very interesting ally for the players should they also be going after the cult.
A section on Covens, including rules for Elder Covens, four new coven types, three new non-evil coven types, six items to be used by hag covens, and descriptions for six sample hag covens. The different coven types (if you don't know, coven types are alternative coven spell lists that are decided by the coven's goals) aren't especially interesting, just lists of spells themed around different things like blasphemy, despair, or fate. The rules for elder covens are of course welcome and good for any higher-level hag encounters you may want to make. The new coven items are also good if you want to make a more challenging coven, and the Brew of Trouble in particular is a great plot device. The sample hag covens are all quite good, though they vary in terms of detail. The Daughters of Mahogra (three hag sisters seeking to steal the heart of the ocean at the behest of their mother's ghost and of course trying to undermine and manipulate each other along the way) have a lot of information about their goals, personalities, and lair, and would make a great late-game threat especially if you're in a seafaring campaign, while Mondiwr, The Blue Coven (A trio of ancient sea hags who have fused into one conciousness spread across three bodies), has only a single paragraph of fluff.
10 new hag types, all of which are interesting, flavorful, balanced, and fit well alongside with the official hags. I won't talk about each individual type, as the desription on the store page gives a brief description of all of them. There are also rules and examples for Elder Hag variants of each type, all of which are very interesting. My favorite new hag type is probably the Deemves hag, since the idea of a fiend so insufferably bureaucratic that even devils can't stand them is just very funny.
32 new hag-related monsters, from flying swarms of cutlery to rats made of ash and ember. All of the monsters are interesing and balanced, with a few in particular immediately making me think of all the interesting mechanical or storytelling role they could fill.
6 unique hags and those that serve some of them, including Baba Yaga and her hut; Malagar the Hag Countess, former ruler of Malboge; and Black Agga, a fanatical high priestess of the trollish god of cannibalism. All have lengthy, well-written descriptions and interesting, well-balanced statblocks, and would make for great higher-level antagonists.
In conclusion this product is a massive amount of high-quality material and the fact that it is only $8 is absurd considering all of the content. There are quite a few typos, but they're mostly minor and easy to ignore, and the writer is fixing any that get pointed out to him. All around an excellent product that is more than worth the price.
[5 of 5 Stars!]