On the book I'm currently messing with, I added in that owl selector with a 0.6 top margin:
Code:
* + * {
/* Lobotomized Owl Selector - what to do any time two objects follow each other - limit to margin-top */
margin-top: 0.6em;
}
and pulled out all my bottom- and top- margins elsewhere. It worked without problem.
In the Calibre editor viewer, I could see the changes to object spacing as I changed the top margin value. Unfortunately, on my Forma, I have to connect/copy/disconnect/open before I can see changes. So, nothing any different really leaped out at me one way or another.
I also removed my top and bottom margin settings in all but my special cases and looked at that. In the Calibre editor preview (i.e., realtime changes), it looks fine without any t/b margins set. Though, the paragraph spacing looks like it might be a bit bigger than what I'd previously had it manually set for. On my Forma, it also looks fine. And, similarly, the paragraph spacing looks like it might be bigger than I had before (my Forma's line-spacing is set all the way down to 0).
Based on the above, I'd probably agree with everyone here and just remove the top/bottom margins from everywhere in my CSS except where I specifically want some different spacing. But, I think I might keep that owl construct in there and play with it some more. Without the top/bottom margin settings, the default spacing seems a tad big for me. I might just use the owl to make it smaller all around.