Thanks! Are the latter novels any good? Or are they glorified fanfics?
I would recommend you read them all. Chronologically they are arranged as:
Young Bond - Charlie Higson. These are set in the 20's-30's when Bond is a teen and it expands upon all the biographical elements that Ian hinted at. You saw his family, home, school, friends, the "incident" with the maid that got him kicked out of private school.
Bond - Ian Fleming's Books.
Colonel Sun - Robert Markham (Kingsley Amis). Amis was Ian's friend and even helped edit TMWTGG when Ian's health was failing.
John Gardner - His books ran in the 80's=90's. His Thing was to continue where Colonel Sun left off but ignoring the fact that Bond was born in the 20's. This is the point where they stopped refering to when he was born in the books or stopped referencing WW2 and just saying that he served in many conflicts as to not tie down the date.
Raymond Benson - He wrote the books in the 90's. He also ignored Amis and Gardner's continuity (except for the female M). This is the guy who write Bond novels like Bond movies, so yes they are the weakest of the entire run.
Devil May Care - Sebastian Faulks. Set a year after Colonel Sun it fits in right between Amis and Gardner and is pretty good if you are reading them in series. If read as a stand along it's weaknesses shows.
Carte Blanch - Jeffrey Deaver. Kinda like Gardner's run where all the biographical information is the same, except that instead of being born in the 20's it's the 80's. Everything else remained the same.
Outside Main continuity -
The Moneypenny Diaries - Kate Westbrook. Not much a fan of these. Take a side charater from the books who was given way too much screen time and create a whole bunch of stuff that didnt happen. It's also written as a diary from MP's perspective so Bond does come up.
Christopher Wood - He wrote the novelizations for The Spy Who Loved Me and Moonraker (because those movies are so unlike the books that they got their own novelization). Imagine that moment in the 70's being a kid walking into a book store and seeing a book that says "Ian Fleming's James Bond in Moonraker" and seeing that shadowy figure on the cover. Or seeing "James Bond's Moonraker by Christopher Wood" with Rog blasting off into space.
You can read them in the order I listed since that's pretty linear. All build upon Ian's continuity or follow it with the exception of Benson who was writing the movie character for the most part. All the biographical info stays the same except the year he was born.