Books, especially technical ones, easily get obsolete within a short period of time. I have several technical books that have recently become obsolete, one of which got obsolete in only three years. This has made me purchase the new editions of some of these books.
There are times when the new editions have significant changes. Others don’t have much changes – mostly reorganization and deletion of sections. I get annoyed when the latter occurs, not realizing it until I have purchased the books.
I usually end up selling or trading in some of these obsolete books on Amazon.com. The money I get isn’t much but it is better than nothing. Obsolete books waste space in my shelves. There are still a number of obsolete books that can no longer be sold and these books are harder to get rid of.
One thing I have stopped doing is to write my name on books I purchase. That way, when I sell them, they still have better value than books that have markings in them.