Someone I follow on Twitter posted a link to a site listing awful library books. These are books currently in public libraries that are just plain awful for one reason or another. Most of them have achieved awfulness simply by becoming totally outdated; for example, this book from 1989 on how not to catch a computer virus or this book on running a farm with wonderful comments about what the farmer's wife does.
Of particular interest are the books on states and countries from 30, 40, 50 years ago, such as this book on the Soviet Union from 1968. (Insert "In Soviet Union..." joke of your choice here.)