My journey of discovery started where a lot of iPad owners likely started, with the iBook app simply because it came with the device. I've used three different apps and I compare them here.
At first, iBooks was a pretty, seemingly functional app that allowed me to read my ePub ebooks. But, since I only had a PC, uploading ebooks that weren't purchases from the iBooks bookstore was confusing and difficult. It had to be done through iTunes (which was abominably slow) and it took a great deal of effort to figure out how it was done (I had to do a great deal of research on Google).
But, I got the books on my iPad and I was reading them. I liked the way the pages turned (and I would frequently play with the page turns as I was reading, slipping my finger back and forth to make it distort). It also showed how many pages were left in the chapter, what percentage you were into the book and how many pages were in the book.
But quickly, I found that, unless I set the font so huge that an old person with vision problems could see it, I couldn't finish a page without the iPad going to sleep. There is no way of changing the duration it takes before it sleeps or turning off this sleep setting in iBooks. Also, there was no easy way of changing the brightness of the screen while reading. Since my eyes are very sensitive, I was constantly wanting to change it but would have to stop reading to do so. I went in search of greener pastures...
After a good deal of research, I tried Stanza and fell in love. The more I used it, the more I loved it. Though it isn't as pretty as iBooks and doesn't tell you the total pages in the book at your current font size, it is far more functional in ways that count.
First off, Stanza is easier to upload books to, even in iTunes. It also allows you to upload books outside of iTunes, including using Calibre (a computer program for organizing ebooks and converting them between formats), email, and direct download from the internet (Email and internet are options for iBooks as well but I didn't learn this until later and it didn't help me for the books I already owned). Hell, you can even access the Smashwords directory directly from the app.
Stanza also allows you a lot more versatility in how you read your books, giving you a plethora of backgrounds and fonts, allowing you to deactivate sleep while the app is open and even allowing you to lock orientation.
Stanza also lets you quickly adjust the brightness of the screen, simply by dragging your finger up and down. You don't have to go to a menu to do this and thus stop reading. I am constantly dragging my finger up and down to fix the brightness based upon changes in lighting conditions where I am reading. I don't even think about it anymore. My finger just hovers there, ready to turn a page or move up and down as needed.
The ability to deactivate sleep and lock orientation are probably my two favorite features of this app. As I said before, unless you're a speed reader, iBooks and Kindle (which I'm getting to) will dim the screen and put the iPad to sleep before you can finish a page. I don't care about saving battery power. I mean, honestly, what are the chances that I'm going to put my iPad down and forget about it? Besides, the machine has ten hours of battery life. That'll last me all day. I think I can afford a few minutes sitting there with the screen active while I stir my dinner.
But my favorite feature is, by far, the lock orientation mode. It might not seem it, but it's a godsend. I don't know about you, but when I read, I fidget and squirm. I might start out sitting upright with the iPad in my lap, but I quickly shift and it's to my right, then I'm laying on my side and the iPad is on it's side as well, then I'm hanging upside down with my feet in the air like a monkey and the iPad in a similar orientation (I'm not even sure that's an exaggeration). I don't care where the floor is. I want the screen to be in the same orientation as my face. I don't want it to suddenly switch on me when I lean over or lay down. I didn't want that with paper books. I don't want it in an eReader.
I'm not going to say much about the Kindle for iPad because, frankly, it is almost identical to iBooks. The only difference is that Kindle for iPad doesn't tell you your progress within a chapter, which is why I am not overly fond of people sending me review copies in Kindle (MOBI) format. It is the worst eReader app I have on my iPad, but nothing else reads MOBI so I'm stuck if someone sends me a review copy from Amazon.
But at least it's better than PDF, which, by the way, Stanza does too.