Maybe you're wondering why 100 pages. It seems so small for a programming book. How can it teach you everything about Elixir with just 100 pages? The honest answer is it can't. But no other book about Elixir can either. And that's perfectly fine. It's naivety to expect to learn everything about a topic as complex as a programming language with just one book, however big it is.
But the question remains. Why not write a 400 pages book that wouldn't cover everything about Elixir either, but at least would have much more content? I could do that, but it would be a completely unnecessary book. We already have great books like that. What we don't have is a book that embraces a smaller length, focusing only on teaching the basic concepts of Elixir.
I believe it's important to offer a book like that because long books can be very intimidating for some people. They give up on reading a book when they find out it has hundreds of pages. They feel it's not worth even start reading it because they don't believe they have the time or patience to finish it. On the other hand, no one is scared of 100 pages. It's much more approachable, and you can finish it even if you don't have a lot of time.
Additionally, this self-imposed limit keeps me honest. You can't fool around and waste pages when you have only 100 of them. Every single word counts. And because of that, it wouldn't be smart to explain very basic concepts. That's why you won't read in this book the definition of variables, integers, and stuff like that. Fortunately, this works great with the target audience: experienced developers who want to dive in Elixir to discover if it's for them.
So if you're the kind of person who prefers small books and wants to learn Elixir in a very objective approach, I believe you will enjoy this book. And if this happens and you find yourself in love with Elixir, don't worry, I'll write similar books about more advanced aspects of Elixir. So instead of not reading a 400 pages book, you'll trick your mind into reading multiple 100 pages books.