This app was mentioned in 19 comments, with an average of 1.58 upvotes
Have a tablet?
Comic Zeal for iDevices
ComiCat for Android.
And once you get it, the entirety of Transmetropolitan is out there too.
Comicat is what I've been using. Supports both local and cloud sync, multiple methods of organizing collections (by folder, by title, and several others). Also has a currently reading section, an unread section and more.
https://play.google.com/store/apps/details?id=meanlabs.comicat
I've been using an app called ComiCat for several months now and I'm extremely happy with it. I've tried most of the major ones out there (including the one OP posted), but found most of them lacking.
I use an app called ComiCat on my android tablet and I think it's pretty awesome. It has a ton of customization features for the "reading mode" so it adapts to different size screens pretty well, and it also has a "bookshelf" feature which is good for organizing your files.
https://play.google.com/store/apps/details?id=meanlabs.comicat&hl=en_US&gl=US
~~Epub: Moon Reader +~~
~~CBZ/CBR: I personally like ComiCat. I've tried several over the past few years and this one has remained my go-to.~~
I'm an idiot and didn't see the word iPad in your post. Sorry. For epub on the iPad, the iBooks app used to work well for me (3 years ago).
For CBR/CBZ, check out Comic Flow.
Hey so I have tried a few for the last week (I just started reading virtual comics from Google Drive) and I'd be happy to give a brief opinion of the two paid options I'm now waffling between.
ComiCat caches comics you want to read and it's very easy to remove the local copies later. It automatically downloads thumbnails for each issue and assigns covers for nested folders for the series. It's a great visual representation of your comics. It's a bit slow turning pages for me too, especially with bigger files. The zoom function can be a bit wonky.
CDisplayEx has a series display mode but doesn't automatically download thumbnails. You have to download an issue, turn a few pages, back out, and delete it. Then the thumbnail displays. This is an easy process but for a person with a big library would be tedious. The series display doesn't nest folders. IMO the UI is cleaner and the reading experience feels a lot smoother than ComiCat, especially in zooming and turning pages. I had an issue with Google Drive and the dev pushed an update less than 12 hours later fixing it.
Tldr: ComiCat has tons of features and shows pictures of issue covers, CDisplayEx is a smoother reading experience for me. Both allow single issue downloading and deleting. I keep switching back and forth between the two! I hope this helps. CDisplayEx has a free version too.