What are the best book landing pages you've seen?

Is this for a trade book or more something like an training ebook?

For trade, I cannot recall a specific book that had a website that I loved. So, I just started searching for a few popular books from successful authors that have a lot of resources to see what they came up with:

Sapiens - https://www.ynharari.com/book/sapiens
Tribe of Mentors - https://tribeofmentors.com
Unshakeable - https://www.unshakeable.com
Principles - https://www.principles.com

Educated - https://tarawestover.com/book
Where the Crawdad Sings - https://www.deliaowens.com

If nobody else responds, maybe take the same approach (even looking at Amazon's best sellers list) to find some inspiration?

That said, based upon these designs, it looks as though even these successful authors leave a lot of the design/selling of their books to the retailers (i.e. Amazon) instead of investing a whole lot into their own book sites.

For ebooks, try places like Smashing Magazine: https://www.smashingmagazine.com/printed-books/smashing-magazine-print-1/ or A Book Apart: https://abookapart.com/products/expressive-design-systems

Hope this helps!