Spanish child monarchs, male prostitutes, suicidal secret lovers, failed sportsmen, forlorn fiction writers, cold war spies and mariners trapped inside the belly of a giant whale? This is either a glorious caffeine trip or the new Decemberists album. The effects are similar - an initial jittery hesitance followed by joyful spasms. Only here, the comedown is virtually non-existent, and you don't get that wild-eyed look that scares children. Portland's Decemberists are bookish troubadours, roguish seafarers and intrepid storytellers weaving folk and indie pop together with engrossing narrative clarity. Their ambitions in sound and storytelling have multiplied tenfold since the days of the bare but lovingly crafted 5 Songs EP. Castaways And Cutouts was the warm and dreamlike folk laden debut full length, Her Majesty, The Decemberists the more lavish and dramatic follow-up. Picaresque is where we now find ourselves: a record filled with vivid beauty, humour, mock theatricality and opulence by the bucket barrow load.

Recorded in August 2004 in a former Baptist church with Death Cab For Cutie's Chris Walla, Picaresque is possibly the grandest Decemberists offering to date. Having built up a loving fan base (one willing to donate in excess of $8,000 earlier this year when a van of instruments was stolen), the band are now a well established package - the artwork, instrumentation, lyricism and live shows form a world peculiar to them and them only. Whilst the traditional hallmarks are here - Jenny Conlee's delicate keyboards and melancholy accordion flourishes, Colin Meloy's reedy pipes - That Dog's Petra Haden (now a full-time Decemberist) supplies vocals and violin, heard best on the baroque pop of 'We Both Go Down Together', a song that soars with arresting strings and stabs of accordion as forbidden lovers throw themselves from the cliff tops.

Right from the bombastic opening of 'The Infanta', it's clear what a step forward Picaresque is. There are very few tracks here which could easily sit on previous releases, partly thanks to Chris Walla's vivid and inventive production, but also as Meloy's song writing has advanced significantly. 'In bathrooms and bar rooms/On dumpsters and heirlooms/We bit our tongues, sucked our lips into our lungs/But we were falling, such was our calling' sing Portland male prostitutes in the heavenly 'On The Bus Mall' where warm, distant strumming is punctuated with pithy rimshots and fluttering organs. Other new sounds are found on the military pomp and grandeur of 'The Bagman's Gambit' - a Cold War spy mystery, it stampedes through the driving rain of a dark night and climaxes to a wailing, ethereal head, a swelling cacophony of noise with tortured voices hidden inside. Ambitious and inventive, it not only demonstrates Meloy's idiosyncrasies both as a lyricist and a songwriter, but also how far his fellow Decemberists have come since their earliest days.

But with ambition there should be a willingness to make missteps, even if they are relatively minor. 'From My Own True Love, Lost At Sea' seems to be the bugbear that has polarised even the most loyal of fans. Desolate and mournful, it feels like an overlong sketch even despite the curious atmospherics and the sweetly innocent lyrics ('Mr. Postman/Do you have a letter for me/From my own true love, lost at sea?'). Also, depending on the amount of antiquated narrative you can stomach, 'Eli, The Barrow Boy' may grate on all but the Decemberists hardcore. Mostly though, these points are completely overshadowed by the amount of worthy additions to the Decemberists canon on display. 'The Mariner's Revenge Song' is a nine minute honest-to-god pirate shanty with humour, drama and a knowing grin whilst '16 Military Wives' must surely be the most gloriously fun indie-pop song to emerge this year, tackling politico-celebrities with singsong vocals and bombastic brass.

Picaresque is more than an indie-pop album, it's a collection of eleven lavishly arranged acts rife with the whiff of greasepaint and the roar of an adoring crowd, which you should be a part of.