Agreed with the bold.

In my major (marketing), there are a few principles that still hold true (ex. 4 Ps), but the industry changes so rapidly that most of the "best practices" that are mentioned become useless within a year.

The books that I kept after graduating were "leisure" books from a reading or poetry class that I took. I held on to them so that I could re-read them and digest the information without the stress of "OMG I HAVE A TEST ABOUT THIS TOMORROW"

Mathematics major here.
 

I don't think I sold *any* of the books in mathematics major back, but did so for many of the books outside my major. Up until my senior year, I was intending to go to Grad School and so kept them as idea sources for areas of concentration. My senior year I decided I had enough of school and decided to get a job in Computer Programming (which I had sort of kept as a minor)...

In the higher level mathematics courses (beyond Differential Equations) the use of specific textbooks tended to be spotty (the courses weren't necessarily offered two semesters in a row and different profs chose to use different text books.

The ultimate in "non-sellability" was the professor in General Topology (Grad level course) who decided that he wanted to use a book he owned printed in the 1920s as his primary textbook (and yes, this can be done in Mathematics) and tracked down the company who owned the copyright for the book. (The original publisher had been bought out a long time ago). While they weren't willing to print the book, they were willing to let the Professor make copies.

I still enjoy paging through my mathematics text books, but know I won't be able to get too deep in them unless I'm willing to sit down and do the proofs in them. (I'm talking things like Topology, Graph Theory and Projective Geometry).

I've keep my books. Great reference material.

I got rid of all of my books because I hated my majors.

But, when I still liked them, I sold the gen-ed books, like Calculus, and passed the major specific ones down the chapter. I don't know if that's just my helpful nature, but I always felt that younger guys could use my books more than I could.

Keeping my gen ed, music, and education books weren't worth it, but I'm glad I kept my English handbook, atlas (great classroom resource), and children's books.

I think I am selling the child development book. Even if I continue with psychology, I know I don't want to go into child psychology. I hated the class, and it's worth at least $80 on Amazon. Thanks for the advice :)

I kept a few major anthologies (Chaucer, Shakespeare, American Literature) in which I had written in the margins. The works in my Chaucer anthology were published in Middle English and I had translated nearly the entire anthology word-for-word (or phrase-by-phrase), and all of my writing books (creative writing, style books and handbooks, editing, etc.).

Interestingly, I have referred to many of my college "text books" at some point over the past 20 years for both work and personal writing.

When I was a little kid, we use to visit my aunt's in Perth Amboy, NJ. I always stayed in my cousin's room because he was away at college and was in awe of the big bookcase filled with all of his books. My aunt explained that they were his college books and it was the tradition to keep all of the ones in your major.

I also remembered that there was a nice black mug with a gold shield on it at the top of the bookcase, which really impressed me because I was into knights at the time.

When I went to college, my experience was different than Naraht's in that most of my Math courses were two semesters long and there was one book for both semesters. Especially in grad school when I had two semesters of Real Analysis, Modern Algebra, Topology, Mathematical Logic and Numerical Analysis.

I still have all of my Math books and I also have a nice black mug with a TKE coat of arms, just like my cousin.

Do *you* have a young cousin who is into knights? :)

Kinda'. My cousin's son is a Sigma Chi and they are into the Norman Shield thing.