LSD was not discovered until after Kafka's death and it's very unlikely that he tool psychedelic cacti or mushrooms. I think The Metamorphosis was less of a 'whoa trippy I'm a bug' and more of a metaphor for being accepted for what you are, although the book has a rather negative outlook in that regard as Gregod is basically abandoned unloved and left to die by his family.
Regarding Murakami, he used to be my favorite author. I discovered Dance Dance Dance about five years ago and went on to read most of his other stuff with the exceptions of Norwegian Wood and his first four novels or so. Once I got to the point where I felt like rereading some of them (I re read Kafka on the Shore and The Wind up Bird Chronicle) I realized all his works were more or less the same. I love the way he weaves surrealism into the quotidien but I notice it gets repetitive rather fast. This is especially noticeable when you read a book of his short stories cover to cover. Almost all of them follow the plot of a normal guy or girl who has some random thing happen and then some sort of resolution. Even the protagonists are frequently identical.
Anyways, I still love Murakami, but it's been a while since I've picked up a book of his.