It is not unusual for people to keep some of their college texts after college when they go on to work in the field they studied. Usually your work can get quite specific and you sometimes find you need a quick refresher - even if it is just in how to describe what you do to a layman.
I've kept my 1st year physics Tipler for eg and I also have a philosophy 101 text and set of excellent notes on classical mechanics and inverse problems. I keep them for their explanatory value. OTOH: I have also sold texts for the very specific courses - like quantum-optics, which was basically all about lasers.
These days, though, most basic stuff you can get through google.
I'd say keep the books for stuff you cannot google - not for the facts, in other words, but for how they are described. Or just for sentimental reasons. If the latter sounds silly to you, you don't have to worry about it - but if you've sweated and laboured and crawled over broken glass with the book as a guide you may know what I mean.