I just finished that book last week after also avoiding it for a long time. I don't think I've had to look up that many words in the dictionary mid-read in decades.

To your question, the book(s) that put me into a reading slump were the Wheel of Time books. I....don't get the hype around them. I forced myself through to about halfway through the fourth book and gave up. Picking up the Mistborn series catapulted me out of that reading slump before the end of the prologue.