Q: Sharing books.

Do you both sync to the same computer ? If you do then she should be able to sync the books to her device from that - if the books aren't in that computer's iTunes library then connect your device and do File > Devices > Transfer Purchases to copy them over.

If you sync to different computers then again do File > Devices > Transfer Purchases to copy them from your device over to your computer's iTunes library if they're not already in it, or you can redownload them on your own computer's iTunes via the Purchased link under Quicklinks on the right-hand side of the iTunes store homepage. You can then copy them to the computer that your wife syncs to e.g. by right-clicking one of them in the Books part of your iTunes library and selecting 'show in explorer' to find where they are stored on your computer, copying them to a flash drive, and them adding them to your wife'e iTunes library via File > Add To Library (you will need to authorise your account on her computer's iTunes via the Store > Authorise This Computer menu option).

You could potentially log into your account in the iBooks app on her device or on her computer's iTunes and redownload them on that, but that runs the risk of tying her device or computer to your account for 90 days : http://support.apple.com/kb/HT4627

This may help

http://www.mcelhearn.com/os-x-10-9-mavericks-sharing-your-ibooks-library/