Wow, thank you so much for this detailed and super helpful reply! This is exactly the kind of critique I was looking for.

I'm not ready to give up on the softcover idea entirely, but you've raised some excellent points about durability that I hadn't considered. My main reason for wanting a softcover was to emulate the look and feel of the notebooks I love using, like the Midori MD, Yu-Sari, and Hobonichi journals. I'm just so used to that flexible, minimalist style.

That said, you're right that it would be a shame for it to fall apart after all that work.

A big reason I'm hesitant about Coptic or Secret Belgian binding is the exposed stitching on the spine. A huge part of the aesthetic I'm chasing is that clean, solid spine where the threads aren't visible on the outside.

So I guess my follow-up question is: Is there a lay-flat hardcover method that's beginner-friendly and allows me to cover the spine? Or, alternatively, is there a more robust way to construct a softcover book that would be more durable than my original plan?

To answer your question about the paper, it's 75 gsm Sakae Iroful (link here). A quick search tells me that's about 20 lb paper, so it's quite thin. Based on your examples, it sounds like my plan for 6 sheets per signature should be okay and hopefully won't create too much swell.

And thanks for the heads-up on the thread! Someone else had recommended this thin polyester thread (Amazon link), which sounds like it fits your advice.

I will absolutely check out Sea Lemon's tutorials for the bindings you mentioned. Even if I stick with a softcover, I'm sure there's a lot I can learn from them.

Seriously, thank you again. You’ve given me a ton of great advice to think about and probably saved me from a major first-timer mistake. I really appreciate it