Ditto with the iPhone 4S. Been trying to solve it for a month now. Stuck downloading, can't delete, tried reinstalling iBooks and book starts the download automatically and won't stop. Drains battery on iPhone trying to download constantly.
None of the funky solutions found on these boards has worked for me.
Book is on my iPad fine, won't download to iPhone and complete the download. Gets to full blue bar and then goes back to 0% and hangs.