Keep in mind that there are copyright laws, and they apply to all of us.
But, one of my best tips ever is to photocopy the pattern from the book or magazine, and then carry the photocopy around instead of the whole book. You can write on the pattern, highlighting parts, coloring in patternwork, marking off where you've finished, all kinds of stuff.
As far as I can find out, it is perfectly legal to make a copy of a work that you own as long as it is for your own personal use. It seems that you cannot make a copy, then sell the book and continue to use the copy. Then there are the hazy areas of scanning to a disk, and "archiving". Well, those areas are not hazy at all to the writers, publishers, and copyright holders. So, watch yerself! Don't even try to post a scanned copy of a pattern on the internet. It will come back to bite 'cha in the butt.
Now, my Aunt Mary liked to make tiny little pencil notes in her books to remind her of what patterns she had made for whom, changes she made, sizes for people, etc. But, surely it is better to have not lost the book entirely than to have all your notes scattered around in all those books. I would give anything to have some of her books with all those little notes in them. But, after her funeral, a nutty brother of hers trashed them all. They were "worthless" to him.
But, I digress. If having a record of the projects made, etc. is important, maybe you could put those copied pages into a notebook to track the notes? I know that at some point in time my DH is going to "have enough" and go on a cleaning bender, probably throwing away magazines in the process. If a copy of the pattern has been stored with the UFO, is is possible, in theory, to finish it at some later date. So, in the interest of someday conquering my OCD-hoarding disorder, the notebook and copies make it possible for me to let go of some of the mounds of periodicals that surround me.
Library Books: Who in their right mind even imagines that a person, even a super knitter, would be able to finish an entire knitting project before the library book is due?
Magazines: Why do some magazines spread the pattern out over pages scattered somewhat randomly around the magazine? Photo on one page, yarn choice advise on a second, directions on a third, charts on a forth. Oh, and don't forget that the finish up directions might be somewhere else.