What's the best place for storing my e-book online and download and read anywhere on the go? Currently I'm using Google play book but it has a storage limit.
By what you say, i think you have an app that supports all those formats and just need a place for cloud backup of your ebooks?
Well, personal opinion, try MEGA, it has 30 gigs of storage and gives 20 gigs extra if you use your phone number as well.
Or you could try mediafire.
Also, there's a new file storage service named dubox, you can't release your ebooks from there to the forum as we're not assured whether it's totally secured or not, but it gives 1 TB of free storage.
Feel free to check them out and reply if it solved your problem.