The Eyre Affair was freaking brilliant. Metafiction about fiction, metalanguage about language. I was astounded by it. By about the third book in the series, I felt a bit as if Fforde was playing the same notes over and over, and I grew bored with it.
One of Our Thursdays Is Missing decidedly rescues Fforde from sequel-itis. In effect what he has done is go over the top of his previous over-the-top-ness. The written Thursday is standing in for the real Thursday, or perhaps she is not. The relationship between the Bookworld and the Realworld is more complicated than ever. This book's internal self awareness makes confetti of the fourth wall, and to some degree, the other three walls as well.
It's a wild ride, and a great deal of fun. Boring it is not. I'd strongly recommend some previous Fforde before you crack this one.