iPhone 6, me too, maybe they meant 6 minutes not seconds. :-)
...maybe because it's 1.88GB vs 27.5MB (via iTunes)
Unfortunately, Apple didn't fix the bug where you can no longer sync ePubs to iBooks on an iDevice with iOS 9.3.x. For some it is worse as they can't even sync PDFs. At least I was still able to add a Take Control book in PDF to my iPad and iPhone.
Update to my earlier post.
I just confirmed that as part of iOS 9.3, only ePubs purchased from the iBooks Store are allowed to be installed into iBooks (PDFs still work - for now). In addition, iOS 9.3.1 checks and REMOVES any non-iBooks Store book INCLUDING user guides downloaded from Apple Support - Manuals. However, after a third re-booting of my phone, the user guides were restored. But non-Apple sourced ePubs are no longer welcome in iBooks it seems, as they can't be added and if they are already there, iOS 9.3.1 removes them.
Are you sure that you have All Books selected from the pop-up menu at the top? I have all the Take Control EPUBs in iBooks, and they're showing up on all my iOS devices.
It's sitting in my iPhone 5 at 380 MB waiting for installation. But not tonight.
9.3.1 fixed the link hang bug for me. 9.3 has been the worst update I've ever experienced throughout the iPhone parade. I hope it's not a trend.
Apple didn't quite seem to understand the consequences of this bug. For those affected by it, clicking the link for info crashed the updater...
Since I installed 9.3.1 yesterday evening, Safari has twice closed all its tabs when I closed one tab (by cmd-W on the external keyboard). I don't recall this happening in the previous year. Coincidence or conspiracy?