I'm at the very end of Transcending the Mundane, I've collected the blood of all the races and he has opened that special portal. The book is sitting on the pedistal but I cannot activate it to read it.

Is this a known issue? Is there a way to get around this road block?

Or am I doing something wrong?

Maybe the unofficial patch may fix this?

Any help appreciated.

There are a few bugs related to the quest, read: http://www.uesp.net/wiki/Skyrim:Discerning_the_Transmundane The known bugs are listed at the bottom of the page but the whole article might be worth a read to see if you missed anything.

Septimus Signus is supposed to turn into ashes when approaching the Oghma Infinium book. However, there is a bug where the event is not triggered which makes the quest impossible to complete.

• The most reliable solution to this problem is to kill Septimus.
  
• Alternatively, reload an earlier save (before giving the blood to Septimus). If inside, exit the cave and wait for an hour while outside before re-entering. This can fix the event to trigger normally.

The first option should work. I will try it tonight.

Thanks for the pointer!

I think if follow him too closely this can be an issue.