I have some books on CD-ROM. They have no damage, true...but good luck finding a computer with a CD-ROM drive now.

CDs are also at risk of disc rot, which might be a non issue for hundreds of years or fail within 20 depending on the CD and storage.

From a Library of congress study: "The mean lifetime for the disc population as a whole was calculated to be 776 years for the discs used in this study. As demonstrated in the histograms in Figures 18 and 19, that lifetime could be less than 25 years for some discs, up to 500 years for others, and even longer."

https://cdm.link/2017/02/a-generation-of-cds-is-already-rott...

- Assuming the hardware does not change

- Assuming the software does not change

- Assuming the usb device is stored securely and lightly used.

Bit rot is real

Need to store virtual machines with both the operating system and the reader/converter software included. There are lots of bits that can rot...

No, you don't lol. You do realize both the algorithm to decompress the media, and the media as well can be stored alongside, right? Including. any instructions to actually use that media.

Sure, but rewriting software in order to access books is a lot of extra work. I just store the VM containing the necessary tools and make sure it still executes in the new HW+os when they are upgraded.

Formats change. Could you use some disk image formats from old Mac emulators made for the Amiga?

Assuming the book is kept under good conditions, in a humid controller room, with nobody touching it?

Your point is moot. there's a reason we moved to digital media, and why nobody keeps paper copies of everything, aside for last-resort scenarios (which once again includes physical media that nobody ever touches)

Your books will be readable in 20 years. Not so with a USB drive.

If USB sticks are as unreliable as some SD cards, chances are they break after a few years, too.

I have a game that was distributed via an USB stick, and on the rare occasion that I had to reinstall that game, I've always needed to restore a backup copy back onto the USB stick, because the files on the stick themselves were damaged (the USB stick itself is required as some sort of copy protection dongle for the installer).