I think a website is the only viable option - a book is potentially out of date the day after it goes to the publisher whereas a website can be totally dynamic, updateable in an instant.
I tinker with my penny websites on an almost daily basis, changing or adding things as knowledge gets added to from fellow collectors.
The drawback, as has been pointed out, is that a website can vanish overnight or, even if the owner becomes unable to update it and leaves it untouched, it will be no more out of date than a book.
Perhaps the answer is a shared ownership. For example, I have given Jerry the necessary information to take on my own websites in the event of some personal catastrophe.