I am asking because I believe that if you are older than 14 or 15 years old, you should be able to read these books. If you are younger than that, my advice is to wait a few years until you can read them (as time passes for everyone). These books are truly excellent and enjoyable.
Buuuut since you requested it...
The Cuckoo's Calling:
Cormoran Strike is a private detective who is hired to investigate the apparent suicide of a famous supermodel, Lula Landry. He is a war veteran with a prosthetic leg, and he teams up with his new assistant, Robin Ellacott, to solve the case. As he delves deeper into the case, he discovers that Lula's death may not have been a suicide after all. There are lots of twists and turns, and the ending is very satisfying.
Cormoran Strike is hired to investigate the disappearance of a controversial author, Owen Quine. As Strike and Robin dig deeper into Quine's life and work, they discover that his latest manuscript is a scathing satire of the literary world, and many of his acquaintances had reasons to want him silenced. The book within the book (Quine's manuscript) is weird and gross, but also very funny. The suspects are all very colorful characters, and there are lots of red herrings and misdirections.
These are the first two books. Do you want to read about the other ones?