I read this one a looooong time ago, and though I wouldn't call it a 'favorite' read, it's one you tend to remember for whatever reason. It does have a lovely cover -- I have the original 1978 paperback edition, given to me by a friend who was 'done' with soap opera, no matter how gay it might be, and looking for something more along the lines of a gay romp with the verve of Tomb Raider or that Jones dude with the hat and whip, nudge, wink.
The story's set in Paris (which might be a cliché: they don't make wisecracks about "Gay Pahree" for nothing...), and this was one of a suite of gay books issued by Avon back in the days when (gasp!) just the presence in a book of gay characters or situations would make it noteworthy, not to say notorious.
The Quirk is what it is: Parisian gay soap opera! Go into it looking for such content and it won't disappoint. It's also about half the weight of Merrick's later works, so you're done before the "ordinary-ness" of the text can perhaps begin to pall. I did read it a second time many years later, and my original "four star" view of it slithered to three ... because there really isn't anything extraordinary about it to merit a fourth star. And in the forty years since it came out, so very many gay books have been published that, frankly, Merrick is up against insuperable competition in today's market.
It's a nice book, and Merrick writes Paris so well, he clearly knows it ... to me, a firm three stars.