Originally Posted by starrigger
I just did, with my own reformatted Chaos Chronicles omnibus. I tested it on Aldiko on Android, Nook, iBooks on ipad, Kindle (various), Sony, ADE on PC, and maybe something else I've forgotten. It looks good on all. I tested night mode, and I tested changing font sizes. It's not a crap shoot, but you do have to take care with certain things. (Okay, some things are a crap shoot with any ebook, because not all devices display things the same way.)
I don't think I tested font changes, though, except in the Kindle multi-device emulator.
Edit: Okay, I just tested font changes and night mode in ibooks. A-okay.
And -- to yank this back to the point of the topic -- it did require (for the benefit of Aldiko and Nook) having the centered styles tweaked in CSS because that was something Calibre is not set up to do.
As for formatting, what is your preferred way to format an eBook so it looks good on most devices be they a smartphone all the way to a computer with a high resolution screen (1600x1200 or larger).