x review – Ed Sheeran's second album has a broad palette but lacks depth

x, Ed Sheeran's second album, is not even out yet, but Sheeran's fans have already gone forth and multiplied, as per its instruction. One grateful US couple won tickets to a mobile phone event last year, where they were serenaded by Sheeran, author of 2011's multimillion-selling +. The pair conceived later that night. The baby's name is Edelle.

Some doubt about the potency of Sheeran's oeuvre does arise when you learn that this couple already had five children, which is why they needed a night out so badly. Nevertheless, Sheeran, a sensitive guitar troubadour by disposition, is set to unleash this baby-making prowess even further with x, an album three years in the precision tooling, involving a cast of collaborators that spans Snow Patrol and Rick Rubin. Sex Ed, you might say, is in the house.

Sheeran began life as a busker and is now one of the UK's biggest stars in a story that blends vintage graft (endless gigging) and contemporary networking (posting videos on grime channel SB.TV, being friends with One Direction). x's lead single, Sing, is a Pharrell Williams co-write in which Sheeran stops emoting over nylon strings and tries to wet some knickers with a Justin Timberlake impression. Sing has already gone to No 1 in the UK and isn't doing too shabbily in the US either, where months of touring – often with Taylor Swift – have given Sheeran a burgeoning profile. For a guitar man, Sheeran has long dallied outside his genre, so this swerve into R&B is not, perhaps, the act of career brinkmanship that it might first seem. He can't quite cut it as a leading man – he replaces himself with a muppet in the video – but Sing is quite easily the best song on x, probably because it sounds nothing like Sheeran.

A sexual dalliance with another pop star forms the basis of this record's other keeper, Don't. They had a thing going on. Then she slept with his friend. No, it's not about Taylor Swift, Sheeran avers in interviews; they are pals and not more. Ellie Goulding, maybe. More exes litter this tracklist, as befits a man who has made the heart his business. Strummy opener One concerns the same muse that inspired the songs on the multi-platinum +. It's not hard to see why Sheeran's every-person tales of devotion and heartbreak, replete with references to popular pastimes (building Lego, drinking) resonate with the pop-buying public. But tracks such as these don't actually find a new gear for the love song, just new turns of phrase, at a push.

Nina finds Sheeran confessing to another old flame that he is always going to tour; The Man finds him actually questioning his vocation. The second albums of successful artists can often be littered with itinerant war stories and this is no exception. But these two songs pack rhythm and some originality, and the upsides of x include candour, hip-hop scansion and Sheeran's willingness to tackle issues not normally dealt with in the realm of fizzy teen pop. It was addiction on his breakthrough hit, The A Team, and it's Alzheimer's on album closer, Afire Love.

Then there are the love songs. This is where critics and record-buyers polarise. Penning relationship crack for teenage girls is a much-derided art, despite being perfected by the Beatles, but Sheeran's is particularly calculated. Tenerife Sea dwells at simpering length on how wonderful a girl looks in her dress. Photograph is a swelling ballad about keeping a picture of someone "in the pocket of your ripped jeans". The name of the game here may be multiplying, but Sheeran knows where his bread is buttered and that is in writing chick lit, not window-steamers.

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