With the iPhone 4 now available, many people want to use that gorgeous retina display to begin reading books on the go via iBooks. We have looked at iBooks on the iPhone 3GS and on the iPad. How does iBooks compare on the iPhone 4?

The good news is that with the increased speed of the A4 processor in iPhone 4 and the retina display, your reading experience is fast and beautiful with iBooks. Let's look at the processor impact first. Many of us eagerly updated our iPhone 3G and 3GS devices when the iOS4 updated became available and quickly downloaded iBooks from the App Store. Sadly, the performance on of iBooks on 3G devices was, to say the least, very disappointing. So much so that some of our readers uninstalled it immediately and rendered it useless. Others, like myself, had a good experience with iBooks on the iPhone 3GS. Not as zippy as iBooks on iPad, but definitely doable. I even encountered an issue where my impatience led me to believe that iBooks did not rotate into landscape. However, at the end of the day it looked good and performance was adequate.

Now the iPhone 4 steps into the scene. In my use of the app over the last 5 days since the device launch, it runs almost up to par with it's big tablet brother. There is still the initial screen to load the library, but after loading, books open responsively and PDF performance is great. I was able to open many PDFs with large images and file sizes with little problem. Of course, as file size increases, performance may decrease. I don't knock this as a downside since opening large PDF's can take a toll on desktop machines.

Next is the retina display. Does it make a difference? For me, the major benefit of the retina display is zooming in on text. In iBooks, you can't zoom on text in real-time, just enlarge the font. Granted, there are absolutely no jaggies, but does it improve my overall reading experience? I would say yes, but it is not a deal breaker. Where the retina display really shines is viewing PDFs- they are stunning. Zoom in as far as you like and the text looks fantastic. The artwork can too, based on the quality of the PDF. Anything you can do to make the viewing experience more pleasant in a mobile device with a screen size like the iPhone is a bonus. Yes the retina display makes a marginal difference when reading iBooks, but by no means is it a deal-breaker. iBooks on iPhone 4 for PDFs, now that is awesome. If you are reading iBooks on the 3GS, I feel you have a comparable screen-reading experience- even on the 3G for most things, but the PDFs are heads and shoulders above what theses other device can offer.

Syncing between devices is a breeze. I have an active iPad, 3GS and iPhone 4. After installing the app on your device and you open it for the first time, it asks you if you want to sync. After choosing yes, the device stealthily syncs in the background, you don't have to hit a button or anything. A spinning "gear" appears in the top right corner by the Wi-Fi and signal icons indicating it is doing its work. It takes just seconds for it to sync and you receive the bookmarks, notes, etc from what you have entered in a iBook and is synced to all devices when you open iBooks on that device.

iBooks for iPhone 4 is extremely polished (well except for a minor bug I encountered. It is captured in the video and screens) and the bookshelf looks amazing with all of the book artwork on the retina display. Text looks good too, though not as amazing as you might think unless you are reading PDFs. Performance is zippy and I think Apple is doing great for their first endeavor for ebooks. Now where is my desktop version?

[Free- iTunes Link]