I've been collecting manga for over a year and a half now, and already, I've gone through the ups and downs of owning them. From my first manga, I was intent on keeping these expensive books safe. I've learned a lot from the day I bought that first manga to the last one I bought.
1. Keep them out of direct sunlight.
The sunlight will cause the colour to fade. You might go to a store and pick one up with an orange cover, but when you compare them to ones on the internet, the original colour could actually be red. For this reason, you should also check what the original colour the manga is on the internet before buying it.
2. Keep them upright.
Manga were meant to be kept like this:
and not meant to be kept stacked. Uneven weight distribution could cause the manga to bend.