My first book I read in Norwegian was an Erlend Loe novel with English annotations. It took me a couple of months and was painful to read, maybe a page or two each day.
My next book was Kurtby, also by Erlend Loe, more of a children's chapter book. It took me about 2 weeks, and was a bit less painful.
I got another Loe book, Fisken (a gift to Maggie from Frøy), and read the first half in an hour on the airplane to Oslo, and the second half on the airplane returning. No pain at all!