The novel is not unreadable, it is enjoyable for the Bond fans, but it is far from being one of the best in the series
Mr. Fleming realized that after World War II, England was no longer the world power it once was and lets it all out on the page in a dialog which must have been torturous to write between Bond and the head of the Japanese Secret Service.
On Her Majesty’s Secret Service by Ian Fleming is a top notch thriller is the second of what has become the “Blofeld Trilogy”, preceded by Thunderball (book review) and concluded with You Only Live Twice (The Spy Who Loved Me was written in between but is not included in the trilogy).
Thunderball by Ian Fleming begins with M, MI6’s head, sending James Bond, our hero, to a two week vacation in a health clinic due to poor health caused by lots of drinking and smoking sixty cigarettes a day.