@Madratter. My personal opinion is that levels range from beginner to medium advanced. If you are a really advanced user and are not interested in the reference guide, then you probably will find a nugget of wisdom here and there, but not more.
The book restricts itself mostly to the standard tools of PI (plus describing a few scripts) with a thorough walk-through and explanation as to why and has on top of that keyboard shortcut lists and pixelmath expressions. Rogelio does not advocate to do everything to an image just because there is a tool for it; he gives his personal opinion on what to do when and what not. In contrast to this, the Warren Keller book (2nd edition) has much more script information. These books differ in style and didactic approach and I have read and enjoyed both and learned a lot by reading different perspectives.
Having said all that: Books are cheap. The digital copy of Mastering Pixinsight is $25,- It is more the time invested that counts. Books for me are efficient in that respect. I know of no (e)book that contains really advanced stuff, say writing scripts for PI or advanced pixelmath trickery.
Edited by AarondeVries, 23 October 2020 - 09:48 AM.