Of course you should read the whitepaper of Bitcoin to begin with 
then I would also recommend to spend your time in understand the biggest projects, which are opening the doors for a lot of ideas such as Ethereum, Stellar, Neo, EOS, QTUM etc. and try to understand the differences. Moreover, I would also read Zilliqa and Quarkchain whitepapers for understanding their visions of implementing sharding technology. And of course before investing you should definitely read the whitepaper of the project you are interested in.
then I would also recommend to spend your time in understand the biggest projects, which are opening the doors for a lot of ideas such as Ethereum, Stellar, Neo, EOS, QTUM etc. and try to understand the differences. Moreover, I would also read Zilliqa and Quarkchain whitepapers for understanding their visions of implementing sharding technology. And of course before investing you should definitely read the whitepaper of the project you are interested in.