I have always hated the wide margins on a kindle but I recently gave the Oasis a go and used calibre to convert books to AZW3 using
html {
margin-right: -60px;
margin-left: -60px;
}
in the Look & Feel, Styling, Extra CSS.
This together with hinted ChareInk font as mentioned in the post above works perfectly for me. I also use the FONT_RAMP to alter the line sizes
https://www.mobileread.com/forums/sh...0&postcount=50
Saying that I would like to reduce the bottom margin but you cant have everything.