Tutorials and programming articles provide excellent resources for learning languages & frameworks but as a professional developer, reading official documentation or a Book always consider as a Good practice because Programming Books are normally written, and go through an attentive inspection process, by professionals of the software industry, so they should be considered a more authentic source.
Learning pace & process of Every person is different. In this article, I’m not convincing you that you should always use a Book & stop learning from tutorials, as Tutorials provide a complete solution of a programming problem whereas books can only give you basic concept & you have to implement your required solution. Still, I think implementing what you have learned from a tutorial or by reading a book will make you more comfortable and productive in the long run.
We have compiled a collection of some great .Net Core books. You must have a look at this list.