Not one but two typos in a single sentence. Which is particularly egregious, because that's the first sentence in a section that used to be its own product (Treasures) -- so you'd think somebody would have noticed them. Another repeated error is the way all the even page numbers appear on the wrong side of the page (toward the spine, instead of toward the edge). But for all the typos (and the procession of small errors is both constant and unending), the first three sections of the Omnibus (classes, magic items, and monsters) are fairly clear and readable. The mistakes don't muddle the meaning, and the style is light and quick to read.

The first section is classes, and the classes are pretty solid simplifications of the more complex AD&D versions. Most of the expected class abilities appear, but are expressed in just two or three sentences. Removing some of the less iconic abilities into a house rule section at the end of each writeup is also smart, because it keeps the core as straightforward as possible while allowing the referee to add a bit more complexity. And the consistent use of Lamentations of the Flame Princess-style non-combat checks for many class abilities (abilities are rated from 1 to 5, and you need to roll equal or under that number on 1d6) is a good choice. The same applies to the magic items, which cover a lot of traditional items in a reductionist fashion. But there's also not a lot of brilliant content. The classes are just streamlined versions of the AD&D classes, not reimaginings that bring something new and original to the table.

The second section, magic items, is also fairly dull. Most are familiar, and my reaction to the new ones is more along the lines of "that's nice" than "wow, that's amazing!". For instance, I don't think a "sword of the halflings", which glows and detects evil in halfling hands, is going to be remembered as a classic.

The third section, monsters, is a further step down. The creatures are just reskinned and (usually) somewhat weakened versions of standard but non-OGL monsters (brain lord = mind flayer, oculus = beholder, etc.), but they've already been reimagined in numerous ways in other old school products, so there's no compelling need for them. But the real downside is the attempt to simplify the monster writeups has turned into oversimplification -- it's not clear how a lot of monster abilities are supposed to work.

The three adventures are next, and this is where the editing gaffs become a real problem. The maps are particularly bad -- for instance, the numbers on the map of the wererat caverns are oriented wrong (they probably flipped the map during editing, but didn't go back and replace the numbers, so they're all sideways); some of the numbers are in the wrong place (one number is in the wrong room, and another is equidistant from several rooms in the middle of nowhere); there's a pit that's discussed in the text but doesn't seem to match the map (which shows steps going up and a raised landing); a secret door is supposed to be the only entrance to a room despite a second, ordinary door that's clearly marked on the map and even referred to later in the entry; and there's no compass rose on the map so the directional references in the text are unclear (e.g. which is the door on the "west wall"?). And that's just the first map; the other two modules have similar problems, like miskeyed rooms.

The stat blocks in the adventures (short as they are) are also hurt by the cavalcade of errors, with elements randomly missing from some entries but not others (like hit points or hit dice), and several times it was even unclear exactly how many monsters are in a room.

The text that is supposed to be read aloud to the players during the course of the adventures is also negatively impacted by the typos. While typos in the main text are annoying, they can be figured out fairly quickly because a casual reader can go back, put the pieces together, and mentally recast the sentence. But when they occur in text meant to be read aloud, time is the enemy. Those errors become verbal stumbling blocks turning what should be a smooth, dramatic vocalization into awkward, broken, faltering, incoherent speech. For instance, try reading the first two sentences of location 18 (in the first adventure) aloud, without sounding stupid or confused: "Pressed against the walls of this cavern are lined with barrels, crates, and all manner of supplies. Where wine casks, storage chests, or burlap sacks, this appears to be some kind of storage chamber." Neither sentence makes sense, and since it's not just misspelled words, (which can be glossed over) but the sentence structure itself, the errors aren't easy to fix on the fly.

The adventures are also light on details. For instance, in the first adventure, there's a plague affecting the local village but no description of the sickness (like symptoms, onset time, treatment, or how it's transmitted). The village priest has deduced the plague is coming from the well, but it's never explained how he arrived at that conclusion. And while there's a way to stop the plague (kill a specific monster), there's no mention of how the monster was causing the ailment. In other words, the disease is described in terms of the actions the PCs are supposed to take (go to the well, kill the monster) and not in terms of how it affects the world. Which is terrible for sandbox play, because the lack of concrete details means the players can't brainstorm alternate out-of-the-box work-arounds, or otherwise interact with the situation as if it were part of a complex, imaginary world where anything is possible. Instead, it becomes a mere in-game puzzle, with a single solution.

Each of the three modules are also billed as "deadly" and the introductions encourage players to "think about their actions", but many of the death traps seem random, rather than deserved. For instance, how does seeing another room reflected in the waters of a pool tell the players that even cautiously touching the water with a tip of finger means death, without a save? It doesn't; there's no warning. So it doesn't punish the players for being careless, or stupid. It's just a penalty for doing what the PCs should be doing -- exploring their environment.

Another problem with the adventures is the level range. The adventures are closely linked, and it's clearly expected that the party who faced the first adventure will move directly to the second, and so on. But the PCs in the second adventure are expected to be 3 levels higher than the PCs in the first adventure, and the PCs in the third adventure are supposed to be another 3 levels higher. But since the adventures are short, it means PCs will have to gain a new level every 6 rooms to be prepared for the next adventure, which seems insanely fast. And if they don't (somehow) advance that quickly, they're going to die horribly -- in the first adventure, the PCs will face 1 or 2 wererats at a time, while in the second adventure one of the earliest encounters is with a 16 HD stone golem (or two?) who is completely immune not just to damage from spells, but will be completely unaffected by all the magical weapons that can be found in the first adventure.

The last part of of the book describes Willow Valley, which is both very boring and ridiculously implausible. Sure, most mini-settings aren't historically or economically accurate. But while we've learned to overlook things like how the smallest of hamlets somehow manage to support both an inn and a tavern, or the huge buildings and tiny farms, this takes the absurdity to a new and very distracting level. For instance, Willowford is a small village with 20 buildings. Yet somehow, those 20 buildings (many of which aren't even residences), support an entire bustling dock district where guards mill around with the workers. It's like the authors don't understand the difference between a village and a city. And the valley is described as sedate, out of the way, and unchanged for centuries; yet somehow, there's not just a lumberyard but a camp inside the village limits. Wouldn't those trees have been cut down, many many generation ago?

tldr; Classes are pretty good, monsters and magic items are okay but unexciting, and the adventures are mediocre in concept but absolute crap in execution. Ridiculous number of typos.