This book is the lovechild of Moominland Midwinter and 1984. I would say it's closer to Shades of Grey than it is to Thursday Next. A bit of a slow-burner to start with, but things are now beginning to get going.
I think Fforde has mentioned in interviews that he had the Moomin stories in his mind while he was writing this, and he certainly pays homage with a character known as the Gronk (Moomin fans will remember the Groke who appears silently and who freezes the ground she sits on). However, you should probably not confuse Fforde's Gronk with the one that plays football for the New England Patriots.
And talking of the Groke, a friend sent me this - It's Fifty Shades of Groke.