how can I do this for books that I no longer require, please
Tap the [Edit] button near the top of the app and select the books/PDFs you would like to remove. Then tap [Delete] and you're done! Hope I helped!
Unfortunately, I tried that and they didn't delete [they were free books but I didn't think that would make any difference]. Thanks for your advice
Delete the books from the Books Library in iTunes, telling iTunes to send them to the trash.
Sync your iDevice to iTunes and the books should be deleted from it.
Looking at iTunes Books tells me that Books has moved so that idea does not work either.
Retrieving data ...