The trilogy is complete and all books are in their final updates. I've officially quit Darwin, but the books are and will always be available (yep. Jan 7th, 2026, and they're still available) for purchase, and are so far proving future proof (though you might want to check out the New Debugging Book as well, for some minor catch ups (specifically, I/7, DYLD (chained fixups) and II/12, kernel zones, had some noteworthy changes). Everything else is still just as relevant.