In a word, Buy. In two words, Buy it. In a third word, Now.
I'm a Firearms instructor, including teaching Concealed Carry classes, a gunsmith, and have worked at a gun range for many years. The insights (for lack of a better word) that this gives into gun safety, the operation of firearms, the history of their development, the moral questions posed by certain training regiments, the background of certain firearms laws, its amazingly accurate, spot on. While there are some qualms I may have with the mechanics, I understand that certain liberties have to be taken when trying to instill gun safety and self defense basics. I've seen some reviews for example take umbrage with the ignoring of for example the Glock's trigger safety and other safety mechanisms that would prevent negligent discharges when holstering or unholstering. The problem with these arguments is that it ignores the point the game is making, which is that all it takes is one moment where you don't put all of your attention to the handling of a firearm for you to make the last mistake you will ever make. I don't want to spoil too much, but to give an example of the amazing points the game can make in the mirror, you see your character is a silhouette target, this at first may seem to be simply a quirk but it will feed into one of the tapes you can find which points out statistics from world war 2, where soldiers often had trouble shooting to kill a fellow human. Current military training focuses on ensuring that troops are more prepared for the fact that they will be expected and required to kill in order to survive. One of the changes made was to institute Silhouette targets instead of simple bullseye. The game mentions that this can lead to soldiers no longer seeing the enemy as humans but as silhouettes, to the point where all people become silhouettes, even the one you see in the mirror.
A non spoiler example of attention to detail is that sometimes when you press the extractor on a revolver, not all of the spent cartridges will simply fall out, some will be stuck requiring multiple presses of the extractor rod in order to free them up. That being said, attempting such attention to detail can cause pitfalls. Full disclosure I only experienced one such example, that being that when looking directly up with the cylinder swung out on a revolver, cartridges will fall out. This at first glance was another example of attention to detail, however even spent cartridges will simply fall out. In real life, the use of an extractor on a revolver is necessary because when fired, the cartridge will expand to contact the walls of the chamber and become stuck. It is a small incredibly nitpicky thing to point out, and I point it out not to detract from the game, but in the hopes that it'll be changed. One last thing I wanted to point out is that one of the tapes discusses the laws of gun safety. An example it give is that if you are training at the range and a hot shell casing falls down your shirt, will you be able to keep the muzzle pointed down range, and would you be able to keep yourself from negligently discharging your firearm at a target you were not intending to destroy. I wish I could count the amount of times I had a loaded gun pointed at me while working at the gun range because of this exact event occurring… (And when I get angry at the person, somehow IM THE JACKWAGON FOR GETTING ANGRY BECAUSE YOU POINTED A LOADED GUN AT ME, BECAUSE OH ITS JUST A SIMPLE MISTAKE THAT TOTALLY COULDN'T HAVE RESULTED IN MY GETTING ****ING SHOT!) I could go on for at least another few characters in this review but I don't want to spoil too much of what makes this game so amazing, at least in the mechanics involved.
Now I've seen reviews which point to the incredible difficulty in progressing in the game. I fully agree that it is unbelievably difficult, infuriating, and may or may not have resulted in me breaking one of my computer mice. That being said, the mouse certainly deserved it as it was a manifestation of the threat and was preventing me from completing my training and becoming a receiver. If you are having trouble with the difficulty of the game, one could look up how to access cheats. I do not recommend it though, as the game, while incredibly difficult, is very rewarding. I almost broke a fifth mouse after throwing my arms up in celebration after completing the final stage.
Once again, to summarize this review, buy the game. You will regret not buying it sooner, and if you don't buy it you will lie in bed at night wondering what could have possessed you to pass up such a masterpiece.