Two main themes run through Dr. No: the meaning of power; and the concept of friendship and loyalty. Bond talks about the meaning of power with a number of villains in the series and his conversation with Dr. No shows that No believes that it can only be secured with privacy, quoting Clausewitz's first principle. Of lesser note, as the academic Jeremy Black points out, although it is American assets that are under threat, it is British power, through the British agent that concludes the issue and a British warship, HMS Narvik, that is sent with British soldiers to the island at the end of the novel.
The concept of friendship and loyalty is the second major theme. The relationship between Bond and Quarrel, the Cayman Islander, is mutually felt. Quarrel is "an indispensable ally" who had assisted Bond in Live and Let Die. The continuation Bond author Raymond Benson sees no discrimination in the relationship between the two men and acknowledges that Bond feels genuine remorse and sadness at Quarrel's death.
For the first time in the Bond novels, there is friction between Bond and M in Dr. No, brought about because Bond was nearly killed by the SMERSH agent Rosa Klebb in From Russia, with Love. M orders Bond to take a new gun and sends him on a holiday assignment, which Bond resents. Benson sees M at his most authoritarian in Dr. No, punishing Bond both in terms of stripping him of his gun and then sending him on what was considered at first to be a "soft" assignment.
Rider is one of three women in the Bond canon who have been scarred by rape (Tiffany Case in Diamonds Are Forever and Pussy Galore in Goldfinger being the others). This follows a pattern where the women Bond comes across are somehow different to the norm, although Black points out that this gives Bond an opportunity to help and save both Rider and the others. Rider is described in the book as having buttocks like a boy, which brought a response from Fleming's friend Noël Coward that "I was also slightly shocked by the lascivious announcement that Honeychile's bottom was like a boy's. I know that we are all becoming more broadminded nowadays, but really old chap what could you have been thinking of?"
Benson considers that Dr. No is "a wickedly successful villain", the best since Hugo Drax in Moonraker, while Time magazine thought Dr. No to be "one of the less forgettable characters in modern fiction". The character is like a number of Bond villains, physically abnormal, being six feet six inches tall, with steel pincers for hands, having dextrocardia. Bond considers him to look like "a giant venomous worm wrapped in grey tin-foil."