I also love collecting cool notebooks! Here are my three faves:
* Minimalism Art A5 – The paper is 100gsm, so ink dries fast. It feels really good, and they're cheap enough that I can buy a bunch.
* Rhodia Webbie – The paper is 90gsm and super smooth. Ink dries nicely with most pen tips. I like it for everyday notes.
* Midori MD – The paper is 80gsm, and ink dries a little faster than the others. Plus, it has a nice, simple look.
I bought a bunch of Minimalism Arts last year when they were on sale. They're still one of my favorite notebooks to use with fountain pens because the ink doesn't bleed through. I would totally buy them again.