I tried The Little Friend, but couldn't get into it.
I did like The Secret History, which is an excellent psychological thriller. It is rather like Daphne Du Maurier's Rebecca. Both novels are full of atmosphere, set in picturesque surroundings (Vermont, old college and Cornwall, stately home). Both are well constructed with plenty of suspense. Both are told by a diffident narrator who is out of their depth when they become part of a life that is way above their expectations and experience. Above all both are suffused with discreditable emotions that we would be embarrassed to admit to. In Rebecca it is jealousy and the sense of being out-classed. The narrator's great revelation is that in fact Rebecca was not the marvellous creature that she has always felt inferior to. The climax:- "He had never loved Rebecca". In The Secret History the discreditable emotion is the desire to become part of the inner ring, the in-crowd, of being ready to compromise virtue and sense to be accepted by a glamorous elite, which in more mundane circles would mean risking your brain trying out dodgy drugs. The glamorous elite falls apart, some dead, others living mean existences.
Both end with the narrator in exile, in Rebecca it's a dull hotel in the South of France, in The Secret History a second-rate job in California. These are- not horrible fates, but for the narrators it is a sense of irreparable loss and diminishment.
Excellent psychological thrillers both, but not novels of any great depth.