I started the review of my possessions with my bookshelves, because I've been thinking about doing some cutting there anyway and they are right beside my desk, therefore handy. I pulled a largish pile off without even needing to think very hard, books I've read and I'm done with.
The shelf with craft books is a little more challenging. I'm less interested in knitting books than I was, but when I page through them I still find ideas that I like and don't want to let go of entirely.
Is it worth keeping a book on my shelves if it has a couple of sweater patterns that I may or may not want to refer to, soon or later or never?
No, not really. For me, the answer is no. It's unlikely I'm ever going to need these patterns, because I've discovered that I'd rather wing sweater patterns anyway. I like the sort of "pattern" where you take a few measurements of the body to be knitted for and a few measurements of the yarn knitted up and then use basic formulas to invent a sweater based on those measurements. I'd rather read the knitting in my hands than pattern hieroglyphics, in many cases.
But there are still ideas here I'd kind of like to keep hold of. Because I do pull ideas from other sweater patterns when I'm figuring out what to wing together for myself. And that's when I realized I have a solution all ready.
Nearly every knitting pattern in the known world today is added to Ravelry, and I already have plenty of reference-patterns collected there, patterns that aren't published in books but online. I don't need to keep the books if all I want are the pictures. I just need to bookmark the pictures, something Ravelry makes easy. I get to keep the part I want, and gain something else I want: room on my bookshelves.
It's really easy to run on auto-pilot when it comes to stuff. A typically American answer to "too much stuff" is to simply throw more space at the problem, rather than consider whether the stuff in question is actually necessary or what a person truly values and needs.
With a little bit of thinking, I get to have my cake and eat it too. I get to keep what I really value in these books, and reclaim some empty space. Crispy 2, Overwhelming Stuff 0. Booyah!