I periodically purge my cookbooks. If it isn't being used then unless we have "history, it is a bible of sorts or it has sentimental value it is probably gone or going to be on the next go round:)
About fifteen years ago I purged almost all of my accumulated books, keeping only those that were important to me, hard to find or again, sentimental. I never regretted this and having moved since was very happy to have done so.
The reality is that if you do this almost anything can be replaced online if you have regrets. And, as others have noted, you can buy more.