Microsoft just volunteered one of my computers for the Creators Update, so I thought I would check out the built-in [EPUB] reader in their Edge Browser.
OK, nothing great, I would say.
I "bought" for free one of "their" classics. It downloaded and read OK.
I "for free" downloaded "the same" classic from PG in EPUB format, open it in Edge, pretty much the same reading experience.
CTRL-SHIFT-R turns the EPUB-specific reading features on and off, if anyone wants to play around with this.
No apparent end-user control of margins, interline spacing, as examples a couple of beefs. One-page vs. Two-page-spread reading depends on how wide vs. tall you make your browser window, for another beef.
Etc.