I think the only book I ever literally threw on
the floor was ~Smilla's Sense of Snow~, by Peter
Hoeg. The sad part: I threw it aside when I was on
about the tenth-to-last page. I thought the beginning
was terrific. I could identify tremendously with the
main character; we don't often see novels whose
protagonists are well-rendered anti-heroines in their late
thirties! Unfortunately, the plot inexplicably crossed
genres from "psychological thriller" to "cheesy sci-fi",
while Smilla herself was slowly transmogrified into
James Bond, only without the sense of humor. Sorry,
Peter. I didn't care how it ended any more.