I have insisted my grandson buy "new" copies of all textbooks and that he retain them indefinitely. Since I pay for the books, it's no big deal to him. The idea, of course, is that he build a library of books he has actually used.
I still have most of my college texts and I actually use them from time to time.
What is more interesting is the changes in presentation over the last 4 decades. Math books used to be pretty dry with few illustrations. Today they are filled with diagrams - most in color. A picture is worth a lot...
One bright note: His copy of Stewart's "Calculus - Early Transcendentals" appears to be the standard in the industry and will be used for Calc I, Calc II, Linear Algebra and Differential Equations. It saves a bit of money if the colleges can get together and standardize on a book. Especially one that can be used for 4 semesters.
Sigh.. once again tl;dr
It's really great to hear that. I use my college texts a lot, but then that's texts from 12 years of study. I don't use my undergrad level texts very often, but I do from time to time. And as a lit major lots of those are not references unless you are taking literature and studying writing styles, etc. Or just want to reread it for pleasure. But except for some that have vanished I have a lot of them. I've discovered that my Dad borrrowed quite a number, so they reappear from time to time.
Spatial memory if far more important than is widely recognized. There is a tremendous amount of material that I know is treated on the bottom left side near the middle of a particular book.
My Linear Systems text, "The Fourier Transform and Its Applications" by Bracewell gets used at *least* monthly and generally a lot more than that. About half of that is for my use and about half when explaining some point in a post. I have probably 8-10 other books on the Fourier transform, but I know what's in Bracewell, so it's my first choice. I only go to the others if the matter is not adequately covered in Bracewell.
I have a 5000+ volume technical library. Seven 12 ft shelves hold the bulk of the computer books and the matching shelves on the back side hold the geoscience and mathematics texts. I've bought a lot of the classics, like Watson's treatise on the Bessel function which have seen very little use. Lots of things like that I found at a used book store. But even then I have well over $150K invested. But I made quite a lot of money from having that immediately available. As a literature major I acquired the ability to read with good comprehension at 400-800 wpm. So if a subject arose at work about which everyone was fairly ignorant, a few days later I was the most knowledgeable by far. I could beat my way through 1000+ pages of documentation in a day or two.
The development of my library in current form is an interesting tale. The student bookstore at UT Austin got a trailer load of remaindered textbooks and put them out on a long line of tables made from 4x8 sheets of plywood for sale at $1. The response was amazing. The books sold faster than they could bring them out and put them on the tables. So they got more. This continued for several months and there was a regular coterie that checked the tables several times a day. We got to know each other's interests and would often point out new arrivals that might be of interest to them, provided we didn't want it ourselves. For $1, I'll buy a book on a topic just because I *might, perhaps, maybe* find it useful. These then got just stacked up in a pile on my living room floor along one wall. Looking at the titles one day I realized I had acquired a rather good general technical library. None of these were in any way related to my course work except perhaps as citations and bibliographic entries. This led me to want a general technical library as a personal tool.
After I left Austin I moved to Dallas and for the next 10 years I made the round of 3 Half Price Books locations collecting technical books on every imaginable topic except life sciences. I did get some of those, but very few. I need to correct that. I continued the practice in Houston for 8 more years and if I go to Houston to visit friends I make the rounds while I am there.
The only downside is that a library of that size is a real bear to move. It takes about 3-4 weeks to pack and about the same to unpack and shelve. sorting and packing by size is critical to not having the boxes collapse. The books weigh around 5-6 tons. It completely fills a 500 sq ft 2 car garage and sits on standard commercial library shelving I bought used from a dealer in California. It's more work than moving the tools that overflow my 1500 sq ft shop building to the point of being a major obstacle to organizing it.
I'd like to suggest another conditional requirement; that your grandson start a card catalog of some type on electronic media. I'd love to have an index, but now it would require working full time for a month *if* you could do a book every two minutes continuously for 8 hours every day.
While she was looking for work after joining me in Dallas, my girlfriend spent a full day working on a catalog for me. Then she turned off the computer without saving the file. I never had the heart to ask her to do it over.