I made a rookie error: I saw the film before I read the book.
I couldn't get the image of Pat being Bradley Cooper and Tiffany being (oscar winning!) Jennifer Lawrence out of my mind from then on. I can only speak from the perspective of having seen the film first - and I would definitely recommend you read the book as well.
It soon becomes apparent when reading The Silver Linings Playbook that Matthew Quick has created an imperfect and unreliable narrator in Pat Sharp. Pat has been recently released from a psychiatric hospital, the length of his stay unknown, he is desperate to repair his relationship with his estranged wife - reading the books she wanted and losing weight through drastic measures. He is a man convinced that his life is a movie being directed by God. Pat is certain that whatever has happened in the past God will ensure that he has a happy ending in his life. His estranged wife, Nikki, will come back to him once she is aware of his journey, the journey is writing down and recording so that she can read it all and understand how far he has come. This is until he meets Tiffany, recovering from the tragic death of her husband, Pat finds her very strange. Following him around town on his runs, asking awkward questions, and telling him the truth which everyone is trying to protect him from.
Despite being aware that he is unreliable in his account of past events I found that Pat was relatable: his take wasn't too extreme, he was simply trying to gloss over the bad things and focus on the positives. His family around him, doing the natural thing, and protecting him from himself and the truth yet at the same time weren't a perfect family themselves. His father struggles with the idea of an intimate and close relationship with his son and his mother struggles to be anything but a cleaning lady and cook for the men in her life. It was refreshing to read a book about mental health issues and to see how the family and people around the person affected struggle to cope and understand the illness affecting their loved one.
The film and the book are very similar, to a point... The book, in my opinion, focuses more on the mental health side of the story more than the love story. There aren't always rational reasons or excuses given for the characters' behaviour in the book which I think the film overcompensates for and loses the poignancy of certain moments as a consequence. The Silver Linings Playbook is a subtle story, well told, and an easy read - perfect for the Summer holidays because whilst it's a difficult topic it is well told and uplifting.
I don't feel that seeing the film before reading the book ruined it for me - I had the image of Pat being Bradley Cooper in my mind, which suited me fine, but if you're not a fan of Bradley's (why!??!!) then you might want to give the film a miss! ;)