The Princeton Bitcoin class and companion text are very thorough. One of the crypto-currencies of note highlighted during the class was zerocoin, which adds a layer of anonymity to the blockchain. The Zcash implementation of zerocoin is currently launching in alpha. It may prove an interesting way to witness the progress of a crypto-currency being bootstrapped in real-time. As well as gaining insight into cutting-edge zero knowledge technology, that some believe may become standard in all future crypto-currencies.
https://z.cash/