Imagine Dragons, “Mercury Act II.”

To say Imagine Dragons Mercury Act II is the second part of a double album is an understatement.

The dark Act I was filled with 14 intense and urgent tracks. It detailed how frontman Dan Reynolds‘ marriage came dangerously close to an edge and nearly fell into an abyss, before being saved by the love of his wife, musician Ana Volkman. Weighty stuff.

Now, add to that 18 more songs. That’s nearly three albums’ worth of material. Long story short: There’s a lot to dig into. The mood this time is decidedly different. The first act was brooding and moody, while the second brings a more hopeful tone. It looks like things are looking up for Volkman and Reynolds (they had a fourth child). He references the hard times, but this time doesn’t dwell on the. The tracks are big, bold and anthemic—a return to the stadium-sized percussion for which the group is known.

Opener “Bones” is upbeat and immediate with a deep sense of booming groove. Reynolds matches the mood with his signature rhythmic lyrical delivery and the song is melodic and fun.

“This life is one big symphony,” Reynolds sings on “Symphony.” The song title is less a description of the music than the thread that connects Reynolds’ lyrics, using the various instruments as metaphors for the narrative. The track is light, fun and has a carefree island vibe.

“Sharks” is simpler. It’s still built around infectious beats and melodies, but with more of a breezy acoustic flavor. “I Don’t Like Myself” is about resiliency and overcoming mental doubts. Again, it’s understated and simple, with the focus on Reynolds’ expressive delivery. “Blur” is a surprisingly raw alt-rock track. While by no means a punk song, it has a little bit of an unfinished punky attitude to it and is a change of pace from the more sleekly produced tracks preceding it. Others like “Higher Ground” return to Imagine Dragons’ bread and butter, with Reynolds offering an almost-rapped, highly enunciated rhythmic vocal cadence.

One thing that defines Act II is its seemingly boundless sound. The band covers a wide spectrum of musical territory, and that’s on display in atmospheric ballad “Crushed.” Things turn more freewheeling on “Take It Easy.” It sounds organic, as if a single microphone was set up in a room and the band jammed the song together live. That live feeling brings songs an immediacy and feels more authentic and much less a studio creation. The pace quickens on “Waves,” a mid-tempo acoustic singalong that calls back the island influence that reappears throughout the record.

The mood of the album might be summed up best on “I’m Happy,” about the triumph of coming from humble beginnings and overcoming adversity. Reynolds has a keen ability to write uplifting and positive lyrics with authenticity and not having it come off as overblown.

But Imagine Dragons scale back entirely on tracks like “Ferris Wheel,” which is built on nothing more than lush vocal harmonies and a lone guitar, and sleepy ballad “Tied,” one of the more direct love songs on the album.

“Try as I might/ I can’t get no peace of mind/ But then you came into my life,” Reynolds sings on earnest ballad “Peace of Mind.”

“Sirens” offers slick and nuanced mid-tempo pop built on a solid beat. Then synths come in and mix with a variety of traditional rock instruments.

“Younger” is a vibrant tune that sounds like throwback Imagine Dragons, but through the lens of an ’80s anthem. It’s one of the best moments on the album.

On ballad “I Wish,” Reynolds jumps back and forth from whisper-singing to screaming. The band gets an assist from singer-songwriter Cory Henry on the melodic “Continual,” to which Henry brings his gospel flavor. The band closes the album with the dramatic and soaring “They Don’t Know You Like I Do.”

Musically, Mercury Acts I & II are jam-packed, showing off every side of Imagine Dragons. It may be too much for casual fans, but for those who’ve followed the band since the beginning, that’s a benefit.

Follow writer Mike DeWald at Twitter.com/mike_dewald.