A book to movie adaptation is said to be best when it remains true to the essence of the original source with the brilliance of all the technicians and artists involved. 
 Indian films have very strong bond with literature and Willian Shakespeare is one of such inspiration for a few. Prominently Vishal Bhardwaj adopted Shakespeare's tradegies Macbeth, Othello and Hamlet to Maqbool, Omkara and Haider. Few years befoe Vishal Bharadwaj, down South, one Shakespearean classic was translated to a story in backdrop of Theyyam - a ritualistic art form with men protraying Gods. The movie beautifully depicts the tragedy in Shakespeare's Othello through the life of a Theyyam artist, which till movie came out was not much known to the malayalam movie goers also.

Kaliyattam is about Kannan Perumalayan who plays the coveted Theyyam of Theechamundi who falls in love with daughter of the village chieftain and elopes with her. Perumalayans friend Paniyan who's jealous of him and wants to takeover the role of Theechamundi awaits for an opportunity to betray him. Paniyan conspires with Unni Thampuran who wanted to marry Thamara, for the downfall of Perumalayan. Paniyan feeds doubts into Perumalayan of an affair between Thamara and Kanthan another artist from his group. Paniyan spins the story putting distrust in the mind of Perumalayan, who inturn lives in deep despair because of his love to his wife and in great anger thinking of her infidelity.  Movie continues in the agony of Perumalayan, innocence of Thamara and the treachery of Paniyan and ends as tragically as the original.

Kannan Perumalayan was bought to life on screen by Suresh Gopi. Suresh Gopi till then starred mostly police action thrillers filled with massive punchlines and out of the world expletives - he defined the genre in those times. But his performance in Kaliyattam was completely different and unexpected. It was critically acclaimed and he won the National award for best actor. Lal as Paniyan was excellent, Lal was a director till then as part of Siddique - Lal director duo and Kaliyattam was his debut, which viewer will never feel like. Lal's eccentric potrayal of Paniyan was well appreciated and made him a full fledged actor in the coming years.

Jayaraaj as director made critically acclaimed arthouse movies and also massive chartbusters. Kaliyattam was his first Shakespearean adaptation and it was made as appealing to all viewers. The elements from the original like the small pox scars on Perumalayan, the daunt from Thamaras father to Perumalayan on her betrayal and many more are aptly added to the movie. Jayaraaj won the National award for best Director for Kaliyattam.

M.J. Radhakrishnan captures the vivid colours of Theyyam and emotions of the characters in natural lighting and minimalistic effects. This adds an eerie touch to the scenes, specifically to the climax.

Kaliyattam is one of the best book to movie adaptation and if you are exploring movies with diverse cultural background and strong premises as in the classics Kaliyattam is a must watch.

Side note: There are notes in internet on intersemiotic translations - loosely put as translation of one artwork into another and Kaliyattam has been referred as a great example.