Yes - it took me close to two months to work my way through this book. My previous encounters with Jo Nesbo have been the Harry Hole novels. In Macbeth - Nesbo works so hard at the beginning to get the Macbeth story line woven into his story of corruption and greed in a nameless town - that I had trouble reading more than a few pages a day. 
It picked up midway through - when Lady convinces Macbeth to murder Duncan and his guards. I think part of my issue is that Nesbo focuses so much on Macbeth's actions - and I prefer to pull for the hero - not the evil, murdering character.