It is ingeniously plotted and has an original background - the Turkish community in Germany. The information about that community was interesting. I don't know how accurate it was. They are apparently victims of severe discrimination. Kemal Kamankaya gets gratuitously insulted for his Turkish origin at all turns.
One problem is what the dust-jacket claims as a merit "the influence of Raymond Chandler and Dashiell Hammett is impossible to miss." You can say that again. It begins with the private eye waking with a hangover and breakfasting on coffee and beer. He then goes on to Sachertorte (which Philip Marlowe would not have done) and gets hired by a woman to investigate her husband's murders, which she thinks the police are ignoring because he was Turkish.
I had a problem with some of the dialog which must be due to the use of German slang. I'm not blaming the translator, Anselm Hollo. Colloquialisms are often just untranlatable, but translators should decide whether to tranlate into British or American demotic. People are addressed as "sister" "duckie" and "dearie." I imagine "God almighty, what a skinflint. What's lose for a paltry thirty marks" was something more idiomatic in German. Maybe some of the jokes are funnier in German or maybe they are well-known idioms. For example the character who "snapped his jaws and squinted as if I had poured boiling water on his socks." which made me think of about the only line of German poetry I remember from school "Ich weiss nicht was soll es bedeuten."

As usual, I read this book in the original German, for one of my college courses, so I can't speak for the translation. The style in German is pretty simple, so most of the book should translate well. However, there is a lot of dialogue in some German dialects, and I don't know how that translates into English.

The story is pretty simple. Kemal Kayankaya is ethnically Turkish, but he was raised by a white German couple, so he doesn't feel like he belongs in the Turkish minority. He still looks Turkish, though, so he has problems fitting into German society. A Turkish woman, Ilter Hamul, comes to Kayankaya for help because he's Turkish.

Ilter's husband, Ahmed Hamul, was murdered, and the police aren't investigating. Kayankaya starts working on the case on his birthday (that's where the title comes from) and solves it within three days. The case becomes much more complicated than a simple murder, and involves drugs and corruption, and a very brief look at some of the troubles Turks face as a minority in Germany. That's kind of a bonus, because this is basically a simple, hardboiled detective novel.

Kayankaya is a good example of a hardboiled detective, so if you like hardboiled detectives, you'll like this book very much. Even if you don't, you'll probably enjoy it anyway, because it's well written. I usually don't like mysteries (besides Sherlock Holmes) but I enjoyed "Happy Birthday, Turk!"

If you're looking for a solid, hard-boiled with a twist, try this first book in a series about a Turkish PI living in Frankfurt. Kemal Kayankaya is a detective well-rooted in the genre's requirements, he's always drinking, often a wise-ass, gets his ass kicked a few times, and kicks a little ass, and underneath all the weariness and disgust, has a streak of compassion. Economical in length, the story about murdered immigrants, drugs, crooked cops, and the red-light district translates well from the original German.

As in "Happy Birthday, Turk!", Turkish PI Kemal Kayankaya displays all the attributes of the hardboiled detective: constant drinking and smart mouthing leads to his getting roughed up and underneath all the weariness and disgust, there is a streak of compassion. Although well-translated, this story about an ecoterrorist act mingled with a murder isn't as compelling as the previous book.

Arjouni's hard-boiled Turkish PI Kemal Kayankaya returns for his third story, this one centered in the world of Germany's "guest workers" and illegal immigrants. Germany's racism is played up in this one, as Kayankaya attempts to find a missing Thai woman. As usual, his wise-assedness gets him into deeper trouble than he really needs. There is a subplot with his best friend, Slibusky, which is a little hard to follow, but for the most part it's the smart, quick, read I've come to expect from Arjouni.