Like a lot of romantics, I fell in love with heart books the first time I saw them. No, I'm not talking about the modern version, where you bend two adjacent pages towards one another and push the foredges down to the spine so it makes a heart shape.
I'm talking about the original late medieval/Renaissance-era heart-shaped books, like this one in the Royal Danish Library
When I started bookbinding, I thought binding a heart shape was going to be easy. So I talked about it to my boss, and saw the slow smile spread across his face - the smile that said "It's harder than you think", and "Why don't you make one and get back to me". Well, since then I've made thousands of [rectangular] books, and he's right. The main issue is going to be shaping the thing, because knives and guillotines are really good at cutting straight lines, but not curves. And I suspect that if you printed it (yes, I know this one was hand-written, but bear with me) on rectangular pages and then cut down the sewn textblock you'd have a problem with accidentally cutting into the text. To say nothing of the agony that would ensue if your knife slipped, after all that work.
So my theory, as yet untested, is that if you're going to hand-print it, you rough-cut the shaped pages, fold and sew them in the heart shape, and put it between two shaped boards, clamp them and cut or sand the textblock down so the edges are even. Then you could apply your edge treatment (this one is gilded but I'm not going there, not at first).
This really does sound like a fun thing to try this summer. But I'll get back to you.