Save storage space and make it easier to sort through your collection of e-books by removing old books from the iBooks app on your iPad, iPhone or iPod Touch running iOS 8. The same process applies to each device. If you decide you want to read the book again, you can re-download it at any time for free.
Launch the iBooks app. Select My Books and then tap Select.
Select one or more books that you want to delete from the iPad. A check mark in a blue circle appears in the bottom corner. If you tap the wrong title, tap it again to deselect it.
Tap Delete and then tap the Delete This Copy confirmation link that appears. The selected titles are removed from the bookshelf.
Restoring Deleted Titles
To put a deleted title back on the iBooks bookshelf, tap the Purchased icon and then select Not on This iPad. Scroll through the titles and then click the Download icon beside the one you want restored.