The cryptocurrency world changes so rapidly, I don't think reading a book is the right way to learn.
Bitcoin's official wiki is a wealth of information, including technical information of how bitcoin works under the bonnet.
https://en.bitcoin.it/wiki/Main_PageThere are lots of videos about bitcoin online as well.
Alt-coins are variations on the same scheme, different reward methods, different proof of work algorithms, different rates of block creation, etc.
As always, actually getting down and doing it is a great way to learn. So get a small amount of bitcoins to play with, send it to some place (e.g. an exchange) and send it back.
blockchain.info has a nice looking block explorer, which lets you see your transactions and what you have on your addresses.
