This is a middle of the road regency romance: there is one gaping implausibility in the plot which I don't want to identify for fear of spoiling the story, but if you can suspend disbelief this is moderately entertaining.
Five years before, Miss Diana Hepworth was due to be married to Lord Durling, when his behaviour gave her good reason to break off the engagement. Not expecting to be believed, she refuses to explain why, and retires to the countryside. Lord Durling brands her as a fortune-hunter.
At the start of this book Diana returns to London to be a companion to her cousin Phoebe Lowden who is making her come-out. She refuses to seek a husband herself, assuming that her reputation is irrecoverable.
An early riser, Diana goes out riding in Hyde Park well before most of the ton are out of bed. While doing so, and heavily veiled, Diana meets the handsome Lord Garthdale, another early riser and one of the ton's most eligible batchelors. She refuses to give him her full name, but enjoying each other's company, they continue to meet in Hyde Park for early morning rides.
Meanwhile Phoebe has found a young man to whom she is attracted, and has formed a strong friendship with Lord Garthdale's sister Lady Ellen Thurlow. But then Lady Ellen becomes engaged to Diana's former fiance Lord Durling.
This presents Diana with a huge moral dilemma. Should she tell Ellen why she broke off her engagement to Durling - and will she be believed if she does?
It's not the best romance I've ever read, but I did find it moderately entertaining.