I have this wonderful old book The SCSI Bus and IDE Interface: Protocols, Applications and Programming (2nd Edition). It was published in 1997 but is still available for purchase through Amazon.
The book comes with a floppy disk (that’s right: a floppy disk!). I had to buy a USB floppy disk drive to read it. I have made the content from the disk available in a tarball, here: scsi.tgz.
If you just want to read the files, those are here: