Make sure you have the xSellize source. If you don't go to this post
1. Open Cydia
2. Tap "Sections"
3. Scroll all the way down until you get to "X Books"
4. Here is where a lot of iBooks are located. Just scroll and find the book you want to download
5. Once you downloaded the iBook, it will show up as an icon. Tap on it. It will open Safari.
6. Once Safari opens, tap "Open in iBooks"
7. It will open the book in iBooks. Then you can read your iBook.It works like any iBook.
8. Now you can start reading your new iBook
Note: Not all iBooks will be in the section, only a selection.
No Jailbreak Required Method
Let's say you don't want to jailbreak your device, or your device cannot be jailbroken at the moment. But there is a way to get iBooks even without a jailbreak. This is the method to get free iBooks without jailbreaking.You can get the iBooks on any device with iBooks on it.Make sure you have a computer with internet connection and iTunes. Go to this post to read more.