In my opinion, a well-stocked collection always includes the right literature. Whereby - in these digital times, many things can be found as PDFs, definitely more space-saving - but just not with the right feel.
As with the actual collecting of retro boxes, it also makes sense to limit yourself when it comes to literature - I mainly collect the English editions of Sun Microsystems Press - a special feature here are the books that are all about Java, as they have a fancy coffee hologram.
But there are also some other gems in the Sun Press catalog that don't necessarily relate directly to Sun products, but deal with general topics, such as Cybercareers (Morris & Massie) or a classic by Linda McCarthy called IT Security: Risking the Organization.
As always ... please don't throw them away but send them to me - I'll be happy to pay the postage if I don't have the title on my shelf.