It hasn’t been updated since about 2004. No idea how much has changed since then but the authors have stated they don’t update it not because it’s still accurate but because they don’t need new kernel devs and it’s a lot of work.

There are some things out of date for sure, but the bulk of it is still highly relevant.

When I was first learning to write kernel drivers, I had LDD open on one screen and the kernel source code open on the other. You can usually look for examples in the source that will help you figure out the “modern” ways of doing things. LDD is indispensable for giving you a solid footing so that you’re not wading into the Linux kernel totally unequipped.

Surprisingly most of it still is. My old modules still compile and work as expected.