Since your new office is bound to be vastly larger, you don't really*need* to throw anything out, right? ;-)
I do it a bit differently. After I have not used a book in a year or two it leaves the office and goes to the "stacks", where space will never be an issue. Most periodicals are dumped after a few months. A few* are kept. Real non-fiction books seldom get thrown out unless they are dedicated to some particular software application etc.
Take a careful look at application notes and detailed data sheets for the pre-internet era before dumping them all. After about 1995 or so, nothing much of that sort is worth keeping, but much of the early stuff may never be put in electronic form, and much of it is still relevant, albeit perhaps requiring an update to more modern parts.
Obsolete books filled with run-of-the-mill chips and ASICs from defunct companies are probably the least useful to you, though someone in need of them might be desperate.
Shipping costs would probably dissuade most buyers, but check completed auctions to see. Maybe there are companies who will buy the stuff to scan and sell the information to others.
OTOH, those Byte magazines are probably worth something!
- Circuit Cellar, Dr. Dobbs (only issues of those two that I buy at the newstand), Foreign Affairs (subscription), recent directory issues of about a dozen trade magazines etc.
Best regards, Spehro Pefhany