I think this is a very good update to High Guard; however, I concur with people who would like to see typos hunted out before it goes to print. Here are a few gotchas from the fleet combat chapters. I've categorised them as [MAJOR] if they need to be fixed for the rules to make sense. The others are more typographical in nature.
p107-108. The headers for range of weapons are a bit too low. I'd suggest deleting "Range", and shifting "Short", "Medium", "Long", and "Very Long" up a row. At the very least, the example of the tigress should have all the weapons shifted down two rows, so that they line up with their range attributes.
p107 [MAJOR] the Tigress' Meson Spinal mount should have damage multiple 11,000.
p111, "and is cannot be repaired" should be "and it cannot be repaired".
p111, "are obtained from the table page 111" should be "are obtained from the table on page 112".
p112, in the italicised paragraph, "The effect lasts for one round ... immune to ion weapons" should not be in italics, as it's not part of the example.
p113 [MAJOR], I don't understand what's going on with repulsors. Since we don't know what the attacking ship's Offensive DM will be, I don't see how we could fill in the form. Further, the formula given (defensive DM minus offensive DM) will sometimes result in a negative number (i.e. when the attacking ship's offensive DM exceeds the target's defensive DM).
p116 "the next closest or next furthest" should be "the next closest or next farthest"
p118 [MAJOR], in the example, I don't see why the offensive DM and defensive DM are being used. They are used for attack effectiveness.
p118 [MAJOR], since armour and damage for weapons are both scaled down by 3.5, I would expect the attack effectiveness damage multiples to be much higher. 100% accuracy would (IMHO) give a damage multiple of 3.5, so the best this table can produce is less than half of weapons hitting (1.5 damage multiple). Maybe I'm missing something, but these numbers feel very off.
p119 [MAJOR], since spinal mounts either hit or don't, they should either have their damage multiplied by 3.5 or multiplied by 1D. As written, they're effectively doing damage on an unarmed target as if they rolled all 1s.
p121 [MAJOR] why does radiation reduce turrets, point defence, and EW? That doesn't happen at all in ship combat.
p121 [MAJOR] "Each round, a ship's crew can repair a number of systems affected by Critical Hits equal to its Crew Skill score multiplied by five, subtracting the severity number of the Critical Hit". It's unclear what this means. I think it should mean that each critical hit repaired requires a number of 'points' equal to its severity level, and the ship has a number of 'points' equal to crew skill * 5.
p124 [MAJOR] under attacks, the rules for gauging distance between fleets from the original High Guard book (page 92) are missing (e.g. how to gauge distance between two fleets that are both at very long range but in different sectors).