Ducks has not seen any problem with nested H tags on my PEz (ADE)
I routinely use
h1 Book
h3 Chapter 1
h3 Chapter 2
h1 Book 2
...
(I save h2 for when books have 'Parts' or When the book is now an Omnibus and has its own title, the Parts become the old books name)
h4 is used for books with sub-chapters? ('Meanwhile, back in Philly....')
I have heard rumors that
some (ADE) devices won't show the first H1 if nests follow
The only reason for using any particular H tag is nesting order. Size and weight can be adjusted in the stylesheet (Display on one lane, dang-it!

)