On a PC version.
I just started playing and at the beginning just past the initial dragon attack on the keep. I've followed a man into a house outside the stone tower.
Looking into chests for loot and coming across a lectern with a book about a Bosmer attack on the Kajiit.
While I can turn the pages just fine, I cannot find the key to put the book back down. I did find one to keep in my inventory but I don't care to keep it.
The controls are crap for the PC BTW but it's minor. I can get used to it.
What am I not doing right?

Press tab.

Don't feel bad, the UI is terrible.

Tab.

Tab closes/backs out of menu/etc.

OK. Got it. Thx.
I remapped some keys beforehand. I thought I had hit that key in an effort to close the book.
This is gonna take some getting used to.