"Inferno" (top), "The Da Vinci Code" (bottom-left) and "Angels & Demons" (bottom-right).

With just four novels featuring the lead character Robert Langdon, Dan Brown has made a fortune selling over 200 million copies and three of his best-selling books ("The Da Vinci Code, "Angels & Demons" and "Inferno") have already been adapted into movies.

The first two movies alone, which were directed by Ron Howard and starring Tom Hanks as the symbologist Robert Langdon, were both box-office hits that grossed a combined total of US$1.2 billion worldwide.

Now, seven years after "Angel & Demons" made its last big-screen appearance in 2009, Ron Howard and Tom Hanks are finally returning for the third time with "Inferno" this October. Although, "Inferno" is actually the fourth novel in the series, we can't tell you why Howard decided to skip the Washington based, "The Lost Symbol", which should've been next in line after "Angels & Demons".

Without much ado, as the third big-screen adaptation of the Robert Langdon series is nearing its impending release, this is the place for you to recap everything "The Da Vinci Code" and "Angels & Demons".

Tom Hanks and Audrey Tautou in "The Da Vinci Code".

Prior to the big screen adaptation in 2006, Dan Brown's second novel "The Da Vinci Code" was already an acclaimed bestseller when it was first published three years ago. With the total book sales going at 80 million copies strong worldwide and even translated into 44 languages, the primary success of "The Da Vinci Code" is mostly attributed to Brown's intriguing mix of contemporary thriller and a religious-bound conspiracy theory that alters the history of Christianity, including the hidden truth behind Jesus Christ and Mary Magdalene, as well as the Holy Grail legend. The content of the book drew criticism among many Catholic and Christian groups, but for all the historical inaccuracies and supposed 'absurd' storyline put together by Brown, "The Da Vinci Code" remains a fun read and best treated as a fictional source of entertainment.

Following the huge success of the book, "The Da Vinci Code" initially got off to a false start. Originally thought to be conceived as the storyline for the third season of TV's "24", the idea was rejected by Brown himself when he cited that he has no intention to see his book adapted into a TV show. Then along came Sony Pictures, where the studio was willing to pay US$6 million for the copyright of the book and hired a trio of industry veterans including producer Brian Grazer (best known for producing "Apollo 13" and "Ransom" as well as TV's "24"), Oscar-winning screenwriter Akiva Goldsman ("A Beautiful Mind") and director Ron Howard ("Backdraft", "Apollo 13", "Ransom" and "A Beautiful Mind") to adapt "The Da Vinci Code" into a big screen adaptation.

Blessed with a mammoth budget of US$125 million and featuring two-time Oscar winner Tom Hanks ("Philadelphia" and "Forrest Gump") playing the famous lead protagonist as Robert Langdon, "The Da Vinci Code" successfully made a killing at the worldwide box-office albeit the mixed responses it received.

Paul Bettany and Audrey Tautou in "The Da Vinci Code".

Like the book itself, Akiva Goldsman's adapted screenplay was largely faithful to the source material with Harvard-based symbologist Robert Langdon (Tom Hanks) summoned to assist the French police investigating a ritualistic-like murder of the Louvre Museum curator, Jacques Sauniere (Jean-Pierre Marielle). However, Inspector Bezu Fache (Jean Reno) believes that Robert is the one who killed Sauniere. In order to clear his name, he soon teams up with police cryptologist Sophie Neveu (Audrey Tautou), who happens to be Sauniere's estranged granddaughter. The duo joins forces to decipher the clues surrounding Sauniere's mysterious death. While pursuing the truth, they also find themselves pursued by a murderous albino known as Silas (Paul Bettany), who answers only to the sinister Bishop Aringarosa (Alfred Molina).

Whereas Dan Brown's nearly 500-page novel version of "The Da Vinci Code" is jam-packed with expository dialogues, Goldsman is smart enough to streamline the content while still retaining most of the novel's essence of fascinating clues and puzzles. As preposterous as they may seem, "The Da Vinci Code" does benefit from a "National Treasure"-like puzzles-hunting storyline (even though that movie itself is a rip-off albeit an entertaining one from Dan Brown's best seller). From deciphering Leonardo Da Vinci's (fictional) invaluable combination-box keystone creation of a Cryptex, to seeking answers surrounding some of the historical past such as the Holy Grail legend and Mary Magdalene, the movie is engaging enough as long as you suspend a huge sense of disbelief.

Thanks to the huge budget, "The Da Vinci Code" looks visually spectacular as well with the help of Allan Cameron's lavish production design and Salvatore Totino's sweeping cinematography. Hans Zimmer's score, in the meantime, is rousing enough that it eventually earned the legendary German-born Hollywood composer a Golden Globe nomination for Best Original Score.

Audrey Tautou and Ian McKellen in "The Da Vinci Code".

Despite casting an international roster of recognisable faces, the cast is a mixed bag. As Robert Langdon, you might remember how the critics and viewers back then react to Tom Hanks' distracting hairdo. His performance is far from his best work, but it sufficient enough for the role. Best known for her role in "Amelie" (2001) and "A Very Long Engagement" (2004), French actress Audrey Tautou brings an earthy charm to her character as Sophie Neveu. Ian McKellen provides a solid support with his lively performance as the wealthy historian Sir Leigh Teabing, while Paul Bettany dominates the screen with his frightening performance as Silas.

Clocking at almost 2 hours and 30 minutes, "The Da Vinci Code" feels long even with all the streamlined approach. This is especially true when the pace tends to be erratic while the long-winded ending is sadly muddled.

The first big screen adaptation of Dan Brown's best seller didn't exactly fulfil its massive hype, but still Ron Howard knows how to deliver a decent blockbuster-sized entertainment, and that is more than enough for the studio to warrant a follow-up three years later via "Angels & Demons".

Tom Hanks and Ayelet Zurer in "Angels & Demons".

Following the massive box-office success of "The Da Vinci Code" in 2006, which raked in US$750 million worldwide, it was inevitable that Sony Pictures invested another hefty budget in adapting the next Dan Brown book based on the character of Robert Langdon.

As a result, the same filmmaking team of "The Da Vinci Code" chose Dan Brown's first Robert Langdon novel "Angels & Demons" to be adapted as the movie's sequel. The story again reunites Robert Langdon (Tom Hanks), in a race-against-the-clock situation to prevent the religious cult of Illuminati from executing the four kidnapped cardinals a.k.a. preferiti (preferred candidates) as well as stopping them from blowing up the entire Vatican city with a nuclear bomb-like antimatter known as "The God Particle".

Like "The Da Vinci Code", a huge suspension of disbelief is a must to enjoy this kind of larger-than-life conspiracy thriller. And thankfully, "Angels & Demons" manages to provide a decent level of entertainment with the same intriguing pseudo-history related to Christianity and ancient symbolism. While the action and suspense were executed in standard Hollywood fashion, returning director Ron Howard made a right choice by improving the pace to avoid the same stuffiness seen in "The Da Vinci Code".

Tom Hanks and Ayelet Zurer in "Angels & Demons".

Tom Hanks, who reprised his role for the second time as Robert Langdon, delivers more-of-the-same performance previously seen in "The Da Vinci Code". But a minor credit should be given to him for finally ditching the ridiculous-looking hairpiece worn in "The Da Vinci Code". Israeli actress Ayelet Zurer, who plays the antimatter scientist, Vittoria Vetra, doesn't possess the same likeable charm as Audrey Tautou did in "The Da Vinci Code" but she is fetching enough as Robert's new female co-star.

Although "Angels & Demons" failed to upstage or even match the same financial breakthrough previously achieved via "The Da Vinci Code", the sequel's modest success manages to pave way for more Robert Langdon series.

Fast-forward to 2016, a seven years gap since "Angels & Demons" is certainly a long wait for both die-hard fans and viewers alike. In fact, this also begs an all-important question: Is Dan Brown's conspiracy-bound thriller related to religion and ancient symbolism still matter to today's generation of moviegoers? Whether or not the upcoming "Inferno" would set the box-office on fire again remains to be seen.

"Inferno" opens in cinemas nationwide on 13 October 2016.