Books

Do books have a purpose after thay have been read or just send them to dump ? 

Throw away or show in your display cabinet. 

Who knows, in 7 years or so ched&co might add a mechanic to be able to re-read the books as a DLC if you pay real world money or something else dumb. 

If anything, hold onto them so that you know what ones you've already collected or read.

AFAIK there's no way to tell which ones you've read in the past, so if you forget in the future and are holding onto mission points or hoping for a specific monthly reward for a specific book, it can serve as a useful reminder.

Duh, you can just check your logs for books read.

So the only real thing to do with them is to put them in your display case to show off how many you've read.

Is it even possible to get a duplicate? I don't believe you can. 

They are only useful again if you have the book that mimics your last read book (can only be used once)

You can't dump them, or send them to someone, or delete them. Just put them in your display once you've read them so other people can see how clever you are.

You can easily check your reading history with "Item use Book" in your activity log. I'm also fairly certain that once you use a book, you never see it again as a mission store item, city find or subscription gift, they are strictly one-offs.

They look real pretty in a display cabinet.

Ahh, that's right, thanks for reminding me.

There's so many logs and statistics available, it's hard to remember everything that's saved.