Should you stick with the Sybex 7th Edition?
Or buy the Sybex 8th Edition for the new April CISSP Exam update?
I'd go with the new one, but it shouldn't matter that much. If you want to be absolutely sure of covering all the topics, even the new ones like Internet of Things and Attribute-Based Access Control, then go for the 8th Edition. I found very few differences and a better explanation of concepts in the 8th edition. There's only about 25 extra pages in the new 8th edition than the 7th edition.
I didn't really see anything removed in the 8th edition from the 7th edition, just additions.
If you want to see some of the new topics which are in the April CISSP Exam update, click here:
2018 CISSP April CBK F.A.Q.S
If you want to see the release dates of the new upcoming editions of the CISSP books, click here:
Books for April CISSP Changes 2018
There's about a 5-10% change in the 8th Edition from the 7th Edition from what I have been reading. And I would also like to state that members have been passing the CISSP post-April exam update using the 7th edition.
If you absolutely want to make sure you did not miss any topics, get the 8th edition. The ISC2 has also recommended that the 8th edition be used in your studies, but they will always recommend the latest edition for anything CISSP-related.
I personally would study both the 7th and the 8th, and try to notice the differences myself. This would not only let me know about the new topics and differences, but also strengthen my overall knowledge from making comparisons.
The paid membership section of this website includes videos, practice questions, and flashcards which cover the new CISSP April exam topics.