The Astonishing is set in a dystopian future United States and follows the Ravenskill Rebel Militia in their efforts to defy the Great Northern Empire of the Americas using the magical power of music.

It was inspired by contemporary fantasy and science fiction franchises such as Game of Thrones and Star Wars, as well as Petrucci's observations on the ubiquity of technological automation in modern-day society.

In their effort to match the album's narrative, Dream Theater wrote songs in a wide variety of styles ranging from mellow ballads to their more conventional progressive metal sound.

In mid-2013, guitarist John Petrucci began writing a story for a concept album, presenting it to the rest of Dream Theater about a year later.

"[6] As Petrucci and Rudess felt that the album needed real string lines and choirs, as well as other organic sounds, they enlisted the help of veteran composer David Campbell to assist with aspects of the orchestration and handle the logistics of recording all of the necessary musicians.

[7] Reflecting on the process for Keyboard, Rudess explained, "Our initial thought was, let’s do it all on rock instruments and let David arrange it, but that wasn’t really thinking ahead in terms of who we are.

After a while, Nafaryus bows to the pleas of his daughter ("A New Beginning") and agrees to meet with Gabriel at an abandoned amphitheater called Heaven's Cove ("The Road to Revolution").

While the meeting time approaches ("Heaven's Cove"), Faythe decides that she wants to use the power of her royal status to change the world for good ("Begin Again").

It was described as an "honest-to-God rock opera" by Rolling Stone,[3] and has been compared to The Who's Tommy (1969), Rush's 2112 (1976), Pink Floyd's The Wall (1979), and Queensrÿche's Operation: Mindcrime (1988).

[21] The album's story was inspired by Petrucci's love of fantasy and science fiction franchises such as Game of Thrones, The Lord of the Rings, and Star Wars, as well as his observations on the role of technology in modern-day society.

In an interview with Billboard, he explained, “I was thinking of all of the things now that people used to do that they don’t do anymore because they’re automated or done by robots: lots of jobs, self-driving cars coming right around the corner ... My thought was, 'What would happen if ... music [became] all artificial?’”[4] Clocking in at over two hours in length and containing 34 tracks,[12] The Astonishing is Dream Theater's longest album and was planned as an immersive experience that would be best enjoyed as a full album as opposed to a collection of singles.

[20] In writing music to match The Astonishing's narrative, Dream Theater ended up playing in a wide variety of styles, from cinematic instrumentals to mellow ballads to the band's more conventional progressive metal.

[22] In an interview with Ultimate Guitar, Petrucci specifically mentioned the song "A Life Left Behind", recalling, "[It] starts with an acoustic, kind of proggy riff, which is something we've never done and has a very Yes sort of feel.

[22] Dream Theater began their marketing campaign for The Astonishing in October 2015, prompting visitors to visit their official website to choose between mailing lists for the Great Northern Empire or the Ravenskill Rebel Militia.

[28] In December, The Astonishing was given an official January 29 release date,[3] with multiple special editions being made available for pre-sale including a deluxe set with a handmade NOMAC 3D model.

[31] Upon its release, The Astonishing debuted on many album charts, including top-ten placements in Norway, Hungary, Italy, Sweden, Portugal, the Netherlands, Germany, Austria, and Canada.

[38] Critics were especially complimentary of the band's willingness to write a long, unconventional album, with AllMusic commenting, "Dream Theater have invested in the 'album' concept (and in listeners' attention spans) even as the music biz doubles down on the notion that long-players are merely envelopes to hold singles.

"[20] Rolling Stone echoed these sentiments, concluding, "The results won't please every Dream Theater partisan, nor will they convert the skeptical.

But it would take a hard heart to deny Petrucci, co-composer and keyboardist Jordan Rudess and their mates credit for the boldness of their aspirations and the assurance with which they achieve them.

[44] In their write-up, RTÉ.ie advised, "park the snootiness before pressing the play button because while The Astonishing makes Iron Maiden's recent 92-minute double The Book of Souls look like a Ramones record, it's great fun ...

In their review, Loudwire elaborated, "A concept album with different characters puts a lot of pressure on the vocalist, and James LaBrie lives up to the challenge.

[20] In retrospect, Dream Theater have observed that fan response to The Astonishing was mixed, which the band anticipated would be the case because of the unique nature of the project.

In an interview with Eddie Trunk, John Petrucci explained, "[The album] was so immersed in the story — everything had to do with that — that there was no question that it was gonna alienate certain people that weren't on board with it.

[49] As the band felt that The Astonishing would lend itself well to a live performance, they decided to play the album in full for each show and hired a production company to help with their presentation.

[50] Following the conclusion of the North American leg, the band moved on to South America before returning to the United States for another run of shows, officially wrapping up the tour in December 2016.