At a technical level, the ebook distributed through Kortext is an Adobe Edition PDF. It has DRM applied to prevent directly copying most stuff out of it.
I happen to have the "Check Point Certified Security Administrator R81.10" ebook. It's 698 pages. It has a proper table of contents with sections and hierarchy, so it's easy to navigate. Each chapter ends with some review questions, and most chapters have one or two labs after the review questions. The labs describe what you need to do, and they have screenshots showing parts of the configuration. The last ~20 pages of the book are an appendix with answers to the review questions.
This course book could be used for solo study. It's noticeably better than course books I've seen from most other companies. I still think an instructor-led course is better, because then you have somebody to help figure out what's wrong if you don't get the expected results in a lab.