They’re a lot of fun. Just don’t go in expecting balls to the wall action and goofy one-liners like the movies; as someone else said they’re more spy/detective stories than action adventures. That said, there’s still plenty of action and they do move along at a pretty good clip.
One thing that stood out to me when I went through a period of reading a whole bunch of them is how much they focus on Bond’s likes, dislikes and interests. It’s not just shaken or stirred vodka martinis and Walther PPKs, the books often go into a fair amount of detail about what Bond takes for breakfast, what kind of products or activities he likes and so on.