Oh, Harry Connelly also has a poll open for favorite e-book fonts.
Font does matter! I always forget about this until I’m forced to read something sans-serif, which I hate.
Personally, I type everything in Times New Roman, and convert other people’s word documents to that before I read them.
I’m used to Times New Roman, double-spaced, no extra spaces after paragraphs. That’s what looks right to me. Also, in case you’re curious about such trivia, I also write with N-dashes instead of M-dashes. And I double-space after periods.
Number of times I’ve forgotten to change my N-dashes to M-dashes before sending a manuscript to my agent or an editor: all but once. Number of times anybody has mentioned this little foible to me: zero. Through the magic of find-and-replace, these sorts of things are so easy to change, they’re not worth fussing about. Yes, you can do a find-and-replace to replace all your double-spaces-after-periods with single spaces, if it makes you happy. As far as I can tell, this falls under Things Not To Obsess Over when preparing a manuscript.
I get copy edits with all my italicized words and sentences underlined. The one time I tried to save a copy editor work by switching all my italics to underlining so they wouldn’t have to? They underlined it all themselves anyway with their red pencils. I think this must be a thing for the typesetting or whatever. So now I type with italics so it looks right on the page.