Which is worse? Finding a book you love and then hating everything else you try by that author, or reading a completely disappointing book by an author that you love?
It's like Would You Rather! I love Would You Rather!
First of all though, I think it's basically impossible for an author to write both a fantastic book and then a horrible book. It just doesn't work. I don't think their editor would let them publish a let down of a book. Just saying.
But that aside, I'd have to say that reading a disappointing book by an author that I love would be the "worser" of the two.
I tend to obsess over authors I love. I put them up on a pedestal and make little shrines to them in my closet and I write embarrassing letters to them that I horde away in my file drawers. So having one of my very revered author idols write a bad book would basically ruin my world.
Thankfully it hasn't happened yet. My sanity is in tact.