I'd be interested. I taught myself to write an OS 10 years back (using floppy disks) and it was PITA. I tried it for fun few months back (just for fun) and even today, I find its not so easy. I would expect it to be < 150 pages, shows me how to write a boot loader "safely" to my USB disk and how to do the other interesting stuff you mentioned post boot - especially interfacing with eth0, wifi, bluetooth (and maybe gpu control)