They are certainly worth finding.
I don't know if novelizations do anything for a film's business. I think it's more the other way around. Since Christopher Wood was also a screenwriter for the two films, his novelizations provide extra insight into some of his original ideas for characters and scenes that didn't make it into the final cut. "Spy" includes background information on Jaws. Instead of General Alexis (or is it Anatol

Without going too much into specific details, I will say that Wood's writing style flows with what Kingsley Amis describes as the "Fleming effect". He draws a lot of collective inspiration from Fleming's original novels and character descriptions. Drax looks as Fleming originally described him.
Speaking of "Moonraker" you might expect that the noveliztion would be of the same silly tone that the films sometimes takes. On the contrary, Wood plays it all straight with maybe a slight tongue in cheek at times.
Reading either book will be rewarding to the Bond fan. In fact, you may find yourself wishing similar efforts had been made for the later films up to "Licence To Kill".
-Joe