With “No Time to Die,” the 25th official James Bond adventure, set to open in April, the Bond films — which have appeared at fairly steady intervals since 1962 — make up the longest-running movie franchise in history. Factor in the two unsanctioned entries, the 1967 farce “Casino Royale” and 1983’s “Never Say Never Again,” and the tally reaches almost double the number of Bond books that creator Ian Fleming wrote. And yet the list of Bond flicks that actually hold together from beginning to end is considerably shorter. For every “From Russia With Love,” you get a half-dozen “Octopussys.”

There’s a similar shaken-to-stirred ratio at work in “Nobody Does It Better,” Mark A. Altman and Edward Gross’s “complete, uncensored, unauthorized oral history” of the films. Juicy, previously unreported material abounds, though it’s camouflaged by vaporous paragraphs of superficial commentary and self-congratulation, generally from the biggest names. Contributors with vague credentials like “pop culture commentator” have to earn their place here by being interesting. Longtime series producers Barbara Broccoli and Michael G. Wilson and 007s past and present Pierce Brosnan and Daniel Craig need no introduction, but too often their notoriety equates to a license to bore. Either they don’t have much to say about how they approach their work, or (more likely) they see little upside to actually saying it.

On the subject of the gorgeous but inane 2015 entry “Spectre,” to cite one still raw example, Broccoli showers praise on the universally loved pre-title chase scene-cum-helicopter battle set during Day of the Dead celebrations in Mexico City. But on the more mysterious matter of the film’s terrible latter half — particularly a baffling reveal about the series’ greatest villain, Ernst Stavro Blofeld — she and Wilson are maddeningly silent.

Altman and Gross offer sufficient commentary on each film’s merits to establish their fan cred, but their acknowledgments page is a bit cagey on the subject of which quotes come from interviews conducted by the authors and which ones are repurposed from other sources. The latter is a regrettable necessity, given that so many formative contributors have died, including original producers Harry Saltzman and Albert “Cubby” Broccoli, as well as Terence Young, who directed three of the first four films. The person who gets the most specific thank-you for granting the authors an audience is, of all people, Woody Allen, who played superspy scion “Jimmy Bond” more than 50 years ago in the bizarre parody “Casino Royale” (“a movie he disdains,” the authors point out).

Bond devotees will nevertheless find the lure of new material irresistible. Ray Morton, a film historian and senior writer for Script magazine, offers specific comment on which writers contributed which ideas to recent screenplays — an area of increasing interest to fans over the past 20 years, as high-profile scribes like Paul Haggis, John Logan and Phoebe Waller-Bridge have been brought in to rework the drafts of Neal Purvis and Robert Wade, the screenwriting duo that has worked on every Bond film since 1999’s “The World Is Not Enough.”

Bond directors weigh in, too. John Glen, who helmed all five Bonds released during the 1980s, explains his no-frills methodology, while “A View to a Kill” co-star Tanya Roberts reflects that “he was a terrible actor’s director.” Martin Campbell, who directed 1995’s “GoldenEye” and the superb 2006 reboot “Casino Royale,” spills about which other soon-to-be famous actors screen-tested for the part that eventually went to Craig. Campbell admits that Barbara Broccoli deserves the credit for choosing him, as most of the other decision-makers were initially unconvinced that Craig was the best candidate. And Jeff Kleeman, who was MGM’s executive vice president of production during Brosnan’s tenure as 007, discusses the franchise’s more recent gravitation toward auteurs like Academy Award winner Sam Mendes, instead of the competent but more anonymous filmmakers who directed the films during the series’ first 30 years.

For all its insights, this big book doesn’t have the shrewd editing and diversity of oft-contradictory voices that made “The Fifty-Year Mission,” Altman and Gross’s two-volume oral history of “Star Trek,” so compelling even for casual fans. And the adjective “complete” in the title is obviously a misnomer. The book concerns only the Bond films, ignoring Fleming’s novels and short stories, as well as those penned by other writers after Fleming’s death in 1964. Various Bond comic strips and graphic novels have been published since 1958, predating the film series by several years. In the 21st century, the BBC has produced a marvelous series of radio plays, adapting Fleming’s Bond novels with more fidelity than most of the movies did. They featured, as 007, Toby Stephens, who played the villain in 2002’s profitable but reviled “Die Another Day.” None of these spinoffs receives more than a glancing mention.

Including them all, of course, would probably take another two-volume book. As Tom Mankiewicz, who worked on the screenplays of all four Bond films released during the 1970s, explains, “Sometimes you cram nine hours of an impossible story to follow into an hour and 57 minutes that you really hope works.” Those who’ve learned to embrace the work of sorting and discarding — a skill that being a Bond fan demands — will be rewarded by this frustrating but fascinating book.

Chris Klimek is an editor with Air & Space/Smithsonian magazine and a freelance critic.

Nobody Does It Better: The Complete, Uncensored, Unauthorized Oral History of James Bond

By Mark A. Altman and Edward Gross

Forge. 720 pp. $29.99