Did you mean eBook Search Pro?
From what I can see this app searches free book sources, then downloads them, and opens them into the book reading app of your choice.
The last step would be the important one. Just downloading the book wouldn't do a you any good. And looking to read the book in the eBook Search Pro app would also fail (if an option) when you are out of range, since I doubt the downloads there are permanent (since it means to save them in another app: iBooks, Kindle, or Nook).
The most important step here would be to make sure you choose a reading app, then make sure the book is actually in that app by opening that app, and opening the book. (while still on wi-fi).
At any rate, I've only read the description of the free version of the app, so I'm not certain of how it works, or how well. It's got good reviews, so it should at least be usable.
As a side note, I'm guessing the app's main source of free books is Project Gutenberg. Most of these books are available, for free, in the iBooks, Kindle, and probably the Nook app (haven't used that one in a while).
The main advantage of the eBook Search app is probably just better search tools. And it might have more sources than Project Gutenberg.
You can also go to the Project Gutenberg page in Safari, and download the books form there. Like the eBook Search app, downloading is not enough. You need to do the next step and save the book to a reader. If you want to do this, and don't know how to use the Open In feature of Safari to save downloaded content, let me know. I can give a quick explanation. This post is already getting a bit long.
