I agree. Aside from Watchers, Strangers, and the first Odd book, I can never remember what I read even a couple of days later. Even Snow started to fade away after a little while. He's an easy read, and I generally enjoy the books, but they just don't stay with me. It's weird.
Same here. I like many of his books but they don't stick with me long. I'm always amazed at how much I can remember from Stephen King books that I haven't read for 20+ years but with some other authors, I don't remember much at all.
I call Dean Koontz my airport/airplane author. His books have a great pace and they are easy to read and I find them easy to read in those situations where there are distractions all around. Maybe the fact that I've read most Dean Koontz books on an airplane has something to do with why I don't remember them.