I think this is a great option for a lightweight Fallout game that still definitely feels like Fallout. So far, I've read most of the text closely, skimmed the entire book, and made a character. Some highlights for me were the radiation system and the weapon traits (particularly the automatic and charging traits). The way rad damage is taken and then the mutations that can result from that feels like a really good fit here with an easy to understand system and fun, creative potential with the mutations. The risk/reward of certain weapons because of their traits also adds some really satisfying "crunch" to the game. Roll under systems are often not my personal go-to (I generally prefer the clarity and flexibility of "big number good"), but the mechanics here make it feel really smooth, still satisfying, and able to accommodate variation across contexts. Whenever I get a chance to run a game in the Fallout universe, this is the system I'll be picking up! I might even make some content for it and would love to see others do the same.
One super tiny suggestion that has nothing to do with the game itself: Because it was exported from PowerPoint, the file's "Title" in the metadata is set to PowerPoint Presentation, which is how the tab is labeled if I open the file up in Acrobat or my browser. If you have Acrobat, the fix is to go File --> Properties or Document Properties and there is an editable field for the Title. Clearing this field will make the tab label match the file's name. It was easy for me to do, but not everyone has Acrobat, so having the original files without a title in the metadata would probably ease the user experience a bit.