Few Hobbies and Games require you to do this kind of preparation and studies. The only thing I can compare it to is my wife's books while she is going through her masters degree, but unlike her where she goes through books and and is done with it I keep having to go back.
I'm not a writer so I can just imagine the stacks of Books and reference materials GURPS writers would have set up. This is just my prep for my Modern Fantasy Game and the bunch of posts I have line up which is about GURPS Magic and researching the option and templates players might be looking for my game (as well as tools for me to quickly generate NPCs).
I try to reference the pages every time I mention a rule as a mental exercise. If It wasn't so time consuming I would have the page reference in everything I mention lolz. I use the books so much, since I also collect them and buy them as PDFs what you see are mostly print outs and a photocopy of Basic Set (when basic set first came out with bad binding, I photocopied and bound it and it became my Copy for Abuse and penciled notes while the replacement copy is shelved for collection purposes).
I gotta love PDFs and the freedom to write notes down on the page without some OCD coming over me about writing on the books.
Printing More Books
I have a bunch of stuff to print out again, and printing things out can be pretty time consuming since I can only do it at 30 sheets at a time with the SCX-4200 samsung printer we have. I really have to be organized when I do it since one mistake can mean 30 sheets of paper and $2 worth of printer cartridge powder can be lost in a mistake. It suck to see a huge pile of error pages.
So I just got GURPS Action: Exploits. I didn't get Action: Heroes since it has too high a power level (250 points vs my 150cp PCs) and my influence for Archetypes is different from the archetypes given (drawing inspiration from Wilderness of Mirrors by John Wick) - which means I'll end up remaking the templates anyway. I like 100pt Templates with -50 disads since that's 50pts below my Character Creation parameters. If they are optimized and competent with just 100pts players have a lot of buffer customizing.
I also got Tactical Shooting, which really changes how the Templates are made up for Modern Characters. War Beneath Heaven Campaign is a Secret Magical Setting, so everyone mostly goes on without magic factoring in their day to day. No wonder James was singing so many praises about this book, when I finally got to read it its stuff my Captain has been drilling into us in Airsoft lolz.
There are a bunch of Books I will have to print out again because I seem to have lost the copy when we moved here to Makati (or I lent it and they forgot to give it back... a common situation amongst gamers).
I think I will post more about GURPS Action: Exploits in the future. Particularly running it in Roll20 and how best to approach the BAD system and the Chase Rules. I want to combine the Chase rules with GURPS Spaceships for some vehicle combat rules. I will have to make a bunch of tables and preparations for such.