Here we disagree.
Posting such links further demonstrates to authors including Ralph, that there are plenty who will promote and use digital versions that infringe on their copyright so there is no incentive for them to revise or author new works of value.
If there were a new, updated edition of such volumes I guarantee the market for the first edition would evaporate immediately, but not when there would likely also be a scanned digital version online of the new edition!
100% of the books I posted links to are now out of print.
If you want people to learn how to code for Amigas there is no better way than to give them free documentation.
I could sell my RKRM's, Guru Book and various other Amiga coding books but the main benificary of those sales would be me; certainly not the wider community nor the original authors.