I've only read the novelization of RE3, and I liked it, because as WJ said he does have a different take on things. For example, he explains Mikhail's bad injury as the result of a failed assassination attempt by Nicholai.
Basically the author tries to follow the game but adds her own twists and subplots to them.
Also she's just as out of the loop when it comes to upcoming games as anyone else. As a result newer releases at the time (e.g. RE3, RE Zero) tend to contradict her older books. She does stick a disclaimer saying her novels are non-canon in her newer books though.