I really love that they've decided to make this book which syphons off the rules of 'Mech combat for the game. If you're not playing an extensive game of BattleTech and are just really focused on 'Mech combat, this means you do not have to carry around or flip through the full rulebook which is a much more involved affair.
The rules are well written, but also as concise as can be. There are multiple examples and diagrams drawn to clarify more obscure questions. The game of Classic BattleTech can be quite a bit granular, and this book helps to figure out the clarifying rules for all kinds of different situations. As with any game of this level of complexity there are still a few situations here and there where players will need to make their best judgement call on what the rules might intend, but I think the creators have done a fairly good job trying to think of the majority of situations you could run into, even in more niche situations.
I should point out that to new players, this is not just a hardcover version of the rules you get in the beginner set or the boxed set of "A Game of Armored Combat". The rules ino those box sets are even more stripped down than this book. However, as with most two player games, since those rulebooks have the tables in there, picking up a slightly more expanded rulesset like this is real handy to have. That way both players don't need to pass the rulebook back and forth.