Imagine you're about to walk onto a stage. The performer before you has received overwhelming applause and a loving reception, and this heightens your nervousness. Now then, let's imagine this scenario in terms of the James Bond series. The act who is about to come onstage is Thunderball, and the act before who has won the great admiration and popularity is none other than Goldfinger.
The James Bond series flew to new heights with Goldfinger, thus becoming the "tough act to follow" for the following installment, 1965's Thunderball.
James Bond heads to the Bahamas to get back two warheads that have been stolen by none other than SPECTRE, which holds NATO (probably the only organization in the early Bond films that's not become hilariously out-of-date) hostage for £100,000,000 (cue inflation joke from Austin Powers). Soon enough, he encounters main Bond Girl for this film Dominique "Domino" Derval (Claudine Auger), whom Bond uses to get to her "guardian", SPECTRE Number Two Emilio Largo (Adolfo Celi).
Like any Bond film, there's a scene with M (Bernard Lee), one with Q (Desmond Llewelyn), and one with Bond's CIA equivalent Felix Leiter (Rik Van Nutter), who has a bit of a bigger role in this film. Leiter also had a good chunk in Dr. No, and would figure prominently in Licence to Kill.
The locales, of course, are shot beautifully. It's also pretty awesome when Bond uses his Bell Rocket Belt to make his escape in the pre-title sequence. The character of Fiona Volpe proves to be just as wily as Bond, seeing right through Bond's ruse and managing to have him tied up before he regains consciousness. Luciana Paluzzi is probably one of the only foreign-born Bond girls not to have her voice dubbed by another actress. Her voice, of course, adds to the allure that for a short time traps Bond.
You're probably wondering about what my opinion is on the "shot in the back" scene when Bond turns Fiona in time for her to be shot by her own bodyguard. Personally, the scene makes it clear that Bond sees the shooter, and in my eyes he purposely kills two birds with one stone.
For me, the only notable thing about this film that seemed to drag on was the final underwater fight between the Coast Guard and Largo's henchmen. Still though, Thunderball is by no means a terrible Bond film, or even a film in general. There are certainly worse Bond films out there (*cough* A View to a Kill *cough*), and not watching Goldfinger before this one will probably help your opinion on this film. Sean Connery continues his winning streak here as Bond, though I'm more of a Roger Moore fan overall (not because he and I have the same last name, that's a total coincidence).
So by all means, check it out, even if you're totally biased against it because of Goldfinger. What this film doesn't accomplish, You Only Live Twice does, so enjoy it for what it is. Like I said, there are worse Bond films out there.