Read "Introducing Ethereum and Solidity" to get your feet wet with smart contracts.

Introducing Ethereum and Solidity: Foundations of Cryptocurrency and Blockchain Programming for Beginners  is a light introduction to Ethereum and its built-in scripting  language, Solidity. At 179 pages, this book is not a comprehensive  tutorial about building decentralized apps (also called DAPPS). The book  does, however, provide a very brief overview of developing and  deploying smart contracts on Ethereum. Author Chris Dannen does an  excellent job of including links for more information. The book also has  a companion Web site where you can get the scripts that the book discusses.

Ethereum is Bitcoin’s More Adventurous Offspring

Ethereum promises to be many things that Bitcoin isn’t. Bitcoin led the  way by proving that it’s possible to create a currency without a central  authority, like a government, or gatekeepers, like banks. So if we can  have decentralized money, why not decentralized business models or even  whole industries? Think Facebook without Facebook and Uber without Uber.  There would be no “middleman” collecting a 20% “rent” on every  transaction or sucking up everyone’s personal information so that it  could make money by putting ads in front of us. Ethereum aims to make  decentralization possible by marrying the blockchain with a full  programming language called Solidity. The Ethereum blockchain provides  the trust element required for any contract. The code you  develop in Solidity provides the business logic. To replace gatekeepers,  you can build all of the necessary functionality into “smart contracts”  that you write in Solidity. But while Ethereum enables you to do cool  things with smart contracts, the more complicated code that you have to  write to implement a smart contract is far more likely to expose  security vulnerabilities. In contrast to Solidity, Bitcoin’s scripting  language is much more limited, but it’s also more secure.

The Book’s Content

Introducing Ethereum and Solidity shows you how to install Ethereum’s Mist browser,  which functions as a wallet and a full Ethereum node that you can opt  to run on the real Ethereum network or the Ethereum test net. Since it’s  a full node, you’ll have to synchronize (i.e., download) the entire  Ethereum blockchain. It took well over a day for me to sync the Ethereum  blockchain and a little less for the test net. The book shows how to create some elementary Solidity programs that  you can deploy to the Ethereum blockchain, or rather, the Ethereum  Virtual Machine (EVM). The concept behind the EVM is that it’s  essentially a giant computer that runs across all nodes on the Ethereum  network. To help ensure that people don’t deploy Solidity programs that  run amok, the EVM charges smart contracts a small amount of Ether, which  is called “gas,” for every operation that the code performs. If your  smart contract runs out of gas, then it will stop. You’ll also learn how to set up an Ethereum miner. Your  miner can compete to create, or “mint,” new “Ether,” which is Ethereum’s  currency. But don’t expect to mint a great deal (or any) Ether. Your  home workstation is unlikely to be competitive with today’s  massive-scale miners in solving Ethereum’s current proof-of-work (POW)  puzzle, which is what your miner will have to do to make new Ether. The  book finishes with chapters about Ethereum’s development roadmap and use  cases for potential real-world DAPPS.

"There be monsters here."

In the chapter about futures, Dannen discusses some of the enhancements  that the Ethereum developers are planning. Those changes should enable  the platform to handle more large-scale applications. For example,  according to Alcoin Today,  the entire Bitcoin network can process a maximum of about four  transactions per second while Ethereum tops out at 20 transactions per  second. In contrast, Visa actually processed,  on average, 1,677 transactions per second during 2016, and claims that  it can handle “more than 56,000 transaction messages per second.” So for  blockchain-based platforms to challenge the status quo, the technology  will have to evolve. One way that the Ethereum developers plan to  achieve better throughput is by switching from a POW consensus algorithm  to a Proof of Stake (POS) algorithm. POW ensures that anyone who adds  transactions to the blockchain had to invest in significant processing  power (e.g., build a data center next to a hydroelectric dam in  Iceland). But POW also wastes a great deal of electricity and limits  transaction throughput. In simple terms, POS requires that someone holds  a certain amount of Ether, not solve a puzzle. The Ethereum developers  hope that POS will make it possible to scale transaction volumes more  efficiently. It is important to note, however, that after six years  without any significant compromises, POW has proven remarkably  impervious to hackers. Will switching to POS open a "New World" of  dramatically increased scalability, or will the ever-present hacker  monsters find security holes that they could exploit to damage, or even  destroy, Ethereum. Like Columbus setting sail in 1492, the adventure  entails substantial risks but also has significant potential rewards.  We’ll see in 2018 when Ethereum embarks on its POS voyage.

Recommendation

Reading this book will not prepare you to develop the kind of smart  contracts you’ll need to render Google’s business model obsolete, but at  least you’ll be familiar with the basic concepts of Ethereum and why it  promises to be so disruptive. From there, you can try some of the many  online tutorials, or wait until Andreas Antonopoulos’ Ethereum book comes out in early 2018. Introducing Ethereum and Solidity is, however, an excellent place to start by getting "feet wet."