The book starts with an introduction and then builds on a simple service, step by step, through the chapters. Hence, the readers will benefit by following the flow of the book, unless they are looking for a particular topic.
Downloading the code and running it is always tempting. However, you will benefit more as you type the code out, especially in the initial chapters. The book is written in such a way that the important concepts and code are present in the chapter, thus preventing you from going back to see the source code.
Having said that, do try out the code samples and run them. It makes the principles concrete and easier to grasp.
I hope that you have invested in a good desktop/laptop, given that you will be running containers and VMs on your machine, which take resources, it is good to have a strong piece of equipment to get going.
Refer to the documentation links mentioned through the chapters to expand the knowledge on the frameworks and technologies discussed in the book.
The cloud is a technology that changes very rapidly. Hence, this book stresses on concepts and demonstrates them through code. For example, CQRS is important as a concept, so we have shown implementation on MongoDB and Elasticsearch. However, you can try out the pattern on any other set of databases.