It's in His Kiss by Julia Quinn

Meet Our Hero ...
Gareth St. Clair is in a bind. His father, who detests him, is determined to beggar the St. Clair estates and ruin his inheritance. Gareth's sole bequest is an old family diary, which may or may not contain the secrets of his past .. and the key to his future. The problem is -- it's written in Italian, of which Gareth speaks not a word.

Meet Our Heroine ...
All the ton agreed: there was no one quite like Hyacinth Bridgerton. She's fiendishly smart, devilishly outspoken, and according to Gareth, probably best in small doses. But there's something about her -- something charming and vexing -- that grabs him and won't quite let go ...

Meet Poor Mr. Mozart ...
Or don't. But rest assured, he's spinning in his grave when Gareth and Hyacinth cross paths at the annual -- and annually discordant -- Smythe-Smith musicale. To Hyacinth, Gareth's every word seems a dare, and she offers to translate his diary, even though her Italian is slightly less than perfect. But as they delve into the mysterious text, they discover that the answers they seek lie not in the diary, but in each other ... and that there is nothing as simple -- or as complicated -- as a single, perfect kiss.

This is the seventh entry in the long running Bridgerton series that I have been slowly working my way through, following on from When He Was Wicked. Once again, the style returns to the tones that were prevalent during the early parts of the series - somewhat light and frothy but still with really good dialogue and intensity between the characters. I really loved Hyacinth and Gareth together, and the fact that Gareth is Lady Danbury's grandson was an added bonus as it meant that we got to see plenty of the crotchety old dragon!

Gareth was great! I really liked him. Hyacinth was good too, but for me this novel really was about him. The fact that he was trying to make his own way without relying on his very hostile father, but still knew not to take himself seriously was fantastic!

If there was any note that was a bit discordant, it was that the sneaking around that took place with Hyacinth and Gareth trying to get into his father's house to try and locate a mysterious treasure from his mother's side of the family was a bit much. The other thing that threw me a little was when Gareth was goaded into proposing to Hyacinth. I definitely understood her concerns.

With just one more book in the Bridgerton series (not counting the two Lady Whistledown anthology spin-offs), I will definitely be sad to say goodbye to this family!

Rating 4/5