It is literally sad to see how the topic was derailed from "learning blockchain" to "learning about bitcoin". Blockchain is a way of storing and transmission of data in the form of blocks, whereas bitcoin is digital money and used for transmitting value from one person to another in a decentralized and a trustless way. Bitcoin and Blockchain can better be stated as
"A way of transmitting value created by the people, for the people and of the people"
"A database in a smart way for storing informations which are confidential and shouldn't be changed over time"
Bitcoin is not Blockchain They are two different entities but are dependent to each other. Satoshi created this technology as a way to store his transaction datas and to prevent the double spending problem for his digital money. But bitcoin can be called as the first application of the blockchain and cannot be called blockchain. Today even though bitcoin is
banned in certain parts of the world there seems to be huge hype for the technology through which bitcoin was designed.
If people get this, then their way of approaching the learning of technology would be very much different. You can call banks will adopt blockchain in future, but the statement doesn't make sense if you stipulate "Bitcoin will be adopted by Banks". They are outright differences between both to face critism and hype together. It is quite good and useful if you learn to develop dapps based on blockchain whereas learning about bitcoin doesn't help you much unless you want to become a bitcoin developer.
If you consider Bitcoin and Ethereum, both are different blockchains and has entirely different vision. On top of that, Ethereum cannot even be considered as a currency used for paying goods. If you consider so, that's completely wrong and someone has misguided you for the greater bad on learning the technology.
- Bitcoin works on the basis of Sha-256 and more commonly elliptic curve cryptography and can be considered as a form of money whereas Ethereum doesn't function as a money or does function as a mode of payment for usage of its own decentralized platform for the creation of decentralized applications.
- You can use Bitcoin only as a mode of payment, whereas Ethereum can be considered as a VM working on the basis of Turing Complete mechanism. They can more commonly be used as a programmable personal computer.
- Not all these minimal resources can be considered as a blockchain applications. If you consider IOTA, they have a very different approach towards blockchain and has changed them completely to work on the mathematical principle of Directed Acyclic Graphs. This particular take on technology removes the miners and they the transaction updations are controlled by nodes. Further, the speed of transactions in the IOTA blockchain improves along with its users.
For one to become a blockchain developer or to master the technology reading books based on bitcoin isn't enough or can be considered as a stupidity. You need to master the cryptography, its terms and every aspect of applied cryptography. Unless you doesn't master the cryptography it would be hard to understand blockchain.