This is a lot of 5 paperback Robin Cook medical thrillers, published by Berkley Books.
Included are:
A 1989 novel titled "Mutation".
A 1997 novel titled "Invasion".
A 1999 novel titled "Vector".
A 2005 novel titled "Marker".
A 2006 novel titled "Crisis".
The books are in pre-owned condition with some wear on the bindings.