Mastering Ethereum: Building Smart Contracts and DApps
The book to read if you’re wanting to get into Ethereum development.
The solidity examples are out-of-date. However, Solidity changes so much, the only source which is in-date are the Solidity docs. Instead of seeing the versioning as 0.4.x or 0.5.x, see it as 4.x or 5.x; makes more sense.
I think one of the first things you’ll realize when reading this book is how much more there is to Ethereum. For example, Ethereum is actually 3 layers(EVM/Smart contracts, Swarm, and Whisper) although 2 of the layers never get any mention.
Dr. Gavin Wood is one of the founders of Ethereum and is the developer of Solidity. There is alot of information covered here which isn’t anywhere else. Other books cover smart contract development, this book covers Ethereum.