Two parts 19, one part 21

XL Recordings, out now

Album of the week? This is the event of the year. Whatever anyone thinks of it, the new record from Adele is a surefire smash.

Its first single, Hello, has reached number one in 28 countries. Adele is still surfing the wave of her own success with 21, by far the biggest album of the 21st century in Britain, with sales of 4.7m in just under five years.

Now back in the charts, 21 may soon surpass Sgt Pepper’s Lonely Hearts Club Band, the most popular album from the most popular group of all, which has sold 5.1m copies in Britain in nearly 50 years. Adele, who resents having to pay the top rate of tax, is going to have to lump it for a long, long time, or move her husband and son to Monaco.

So she can’t fail commercially, but, in terms of quality, the signals have been more ambiguous. She is said to have recorded a whole album and shelved it. Her management, usually helpful to the media, withheld 25 until about 44 hours before it reached the shops, which smacked of a lack of confidence.

The track listing reveals that, in the space of 11 songs, she used eight separate co-writers, whether individuals or teams. Yet more, including Damon Albarn and Phil Collins, were tried and ditched: if Adele needs new material for her break-up songs, these two are doing their best to provide it. Hell hath no fury like a frontman scorned.

Hello is a curate’s egg – a high-concept comeback, a mark of Adele’s fearlessness, a gift for the meme artists, but strangely hard to sing, even for someone like her. It tries to rhyme ‘everything’ with ‘healing’ and ‘side’ with ‘times’, and Adele keeps calling her ex on his home line, while also wondering where he is living. Straining to match the songs that propelled her into the stratosphere in 2011, Hello misses their scorching rawness.

It’s the first song here, but not the best. It is trumped by When We Were Young, co-written by Tobias Jesso Jr (a singer, not a pen for hire): an Elton John-ish fictional tale in which Adele imagines going to a party when she’s 50, and running into the inevitable old flame. The chorus is as big as Hello’s, but the song is more coherent.

Adele’s forte is the piano ballad, which provides all the highlights here. I Miss You, written with Paul Epworth, is a simple love song with a complex drum pattern and a storming chorus. Love In The Dark, written with Adele’s bass player Samuel Dixon, adds an orchestra, but still runs on the rapport between the keys and her voice. She could tour with just a pianist and have us in raptures.

Not that she knows it. Something has persuaded her to mix it up, with very mixed results. Send My Love (To Your New Lover), co-written with Max Martin, is a repetitive pop ditty which confirms that if there’s one person who doesn’t need a Swedish hit machine, it’s Adele. Later on, she twice has a stab at a standard, a ballgown ballad: tonight, Matthew, she’s going to be Barbra Streisand. Her voice rises and softens, she gives it her all, but she doesn’t seem herself.

Even one of the piano ballads, Remedy, co-written by Ryan Tedder, falls flat. It’s basically Bridge Over Troubled Water, without the magic or the metaphor. As if Adele spots this, the next track is called Water Under The Bridge, but it’s a limp pop song that would have been better left to Katy Perry.

Adele showed a talent for covers with Bob Dylan’s Make You Feel My Love, but there are no old songs here, just a pile of old titles, from Lionel Richie’s Hello to Little Boots’ Remedy. The one fresh title, Sweetest Devotion, is a decent tune, a soul track that could be about the greatest love of all – that of a parent.

With 25, Adele has gone back to the level of 19: very good in parts. Given the pressure to follow 21, it’s hardly surprising. She still has credit in the bank – along with a lot else.