It is 1927. Agnes Humphries, blunt and opiniated but kind owner and landlady of No. 23 Burlington Square, is in search of a new tenant for the second floor. She has to choose between her young niece Clara Goodwin, nervous widow Mercy Mayweather and bank clerk Stephen Thompson.

Her other tenants are Gilbert, a socially awkward photographer in the attic, and Alexander Gorski, an elderly Polish gentleman and former musician on the first floor, plus the poor Smith family with their three young girls in the basement.

What follows are three alternative timelines in which Agnes offers the room to Clara then Stephen then Mercy. Each timeline concentrates on that tenant, with the others being in the background, however their stories unfold differently each time. At the same time, Agnes's own story is slowly revealed throughout the book.

Even though those timelines are not consecutive, there is little repetition which speaks for the author's talent. In each timeline the reader learns certain things about the protagonists and takes that knowledge into the next timeline.

I enjoyed unconventional Bright Young Thing Clara's story the most. Those who suggest her story is only there for the diversity element can get in the bin. There are three love stories that are being juggled and many secrets being revealed. No one is quite as they seem and everyone lies and hides things. 

Wild child Clara had an indiscretion with a groom - or did she? Mercy's husband died in the war - or did he? Stephen has a respectable job - or has he? What is Gilbert really photographing and why, what secret does Mr Gorski have, and will Jemima Smith ever escape her domestic drudgery? And why did Mr Blandford really die so suddenly? The answers will surprise you.

This is a compelling story about love, loss, friendship and grief, and the emotional impact from turning unhappy people caught in the prejudices of their time into happy ones is high. The last Sliding Doors timeline thankfully gets it right for everyone involved, which I was immensely glad about, as I had grown fond of them all (with one exception). The epilogue is simply wonderful. Highly recommended.