I don't think that tingling is a sign of gelling.

Normally, I would say you stop layering when you have as much information from the book as you Want. However as part of the 12 books towards instantaneous / spontaneous activation I would suggest that you layer and maybe go to rapid read until you feel you have the same level of comprehension that you would if you had read the book regularly.
I'll be looking to see what others think.
Good luck Aaron. 
Iam2 