I finished… that issue of Harta from ages ago!
I read ~one chapter a day. It was pretty fun - I never knew what I was going to get next. Kind of like an advent calendar actually. 
Some thoughts on specific chapters that stood out -
山を渡る -三多摩大岳部録 - It’s really charming how there’s a manga for every imaginable interest or hobby (in this case, mountain climbing). I enjoyed this one (though maybe I just like grocery shopping).
ダンジョン飯 - Seems like a cool chapter, except the reveal at the end didn’t have much impact since I don’t know who or what anyone is.
ハルタビギンズ - A series of 8-page specials. Some freaky stuff in here, geeze
対岸のメル -幽冥探偵調査ファイル- Nice little detective story with some weirdly bold kids
ヴラド・ドラクラ - Double-page spread of… Dracula knitting. Nice.
ふしぎの国のバード - A trek into the jungle to find… a new tree species! Based on this guy. Makes me want to track down some sort of pulpy adventure novel.
涙子さまの言う通り - A murder mystery. I think I was missing some context for this one, but it seemed cool.
That one where they teach the dude how to cook and learn that the spice of life is friendship - You know, I’d probably be happiest if this magazine were a 50/50 mix of mysteries and cooking manga.
ホテル・メッツァペウラへようこそ - The hotel one - pretty cozy
Honestly, I don’t know if any of these on their own were as good as just reading a normal book, but very few of them were bad either, and the variety goes a long way. I’m probably not going to read every issue but I could see myself doing this a couple times a year or something.
I also recently finished 陰陽師 by 夢枕 獏. It’s a collection of fantasy short stories about Abe no Seimei, a historical sorcerer-ish dude from the Heian period. Each story is a spooky little mystery where Seimei and his warrior/musician/everyman buddy Hiromasa solve some sort of yokai problem. Lots of creepy setups, light philosophizing, and men grunting at each other while staring contentedly at a garden. It’s not perfect (Seimei is a bit too good at his job, and the character development is a slow burn) but I enjoyed the book quite a bit and recommend it to anyone who thinks it sounds interesting.