None of his books are rubbish?
Well, lemme put it like this: There is NO author, actor, composer, in general creator of things out there who did not have one or two failures in his/her portfolio. Don't know which books you read so far, but even discworld has some groan-and-threw-it-into-the-corner-worthy ones *coughsunseenacademicalcough*
The majority makes up for it though...