Am I prepared to write a murder mystery? Agatha Christie caliber?

Without seeing how you write, i can't really tell you if you should or shouldn't write a book. But you do seem to have keen interest in this so i say go for it! And you don't have to do a murder to be deceptive. A few things that come to my mind are secret agent, where you can pull the whole double agent thing, possibly someone infiltrates something as simnple as a family and is slowly tearing them apart (check out the movie Stepfather for a similar idea). No one actually has to die for there to be a killer on the loose. It could be even more exciting putting ten people in a building, one is a kilelr and the rest have to figure out who before the killer starts murdering them. But now i'm ranting, so i hope i helped! Good luck!