Just as a heads up, most charity shops will be able to send unsellable books (like old tech manuals) to recycling and get a teensy bit of money for them, so please do ask the shop where you're donating if they'll take them. (I believe the shop where I volunteer gets the princely sum of 5p/kilo for books, so an O'Reilly book will probably be an extra 5p for them and it does all add up!)