The guide says (at the end of Act II). Page 144
“Activate the Lexicon Receptacle so that the Blank Lexicon rests on it”
But how?
When I press E to activate the middle pillar nothing happens. I tried the space bar but all I did was jump.
I have the Lexicon but I can’t Drop it or Activate it or make it a Favourite. In fact I can’t get it out of my Inventory let alone put it on the Receptacle.
Can anyone help please.

I forgot to say I'm playing on a PC

Could you clarify exactly what quest you are on? I do not recall any pillars during http://www.uesp.net/wiki/Skyrim:Alduin%27s_Bane

He means the quest before Alduin's Bane. Discerning the Transmundane was it?

Anyway, the receptacle is to the right, not in the center.

Thank you both very much.
I did mean the previous quest and I hadn't noticed the pillar on the right.
I have finished the quest now.
It's not easy being an idiot.

not many people realize how much effort it actually takes.