How many of his books are based on movies?

Okay, to my knowledge there are 22 books which his films are based on:

Heart of the Country (Fay Weldon)

Metroland (Julian Barnes)

Portrait of a Lady (Henry James)

American Psycho (Bret Easton Ellis)

Captain Corelli’s Mandolin (Louis De Bernieres)

El Maquinista – the machinist – ( ?) This one I think is only in Italian, but I'm not sure

All the Little Animals (? Walker) I can't remember ths guys first name, sorry

The Prestige (Christopher Priest)

Terminator: Salvation (movie Novelisation)
and a prequel: From the Ashes

Little Women (Louisa May Alcott)

Treasure Island (Robert Louis Stevenson)

A Midsumer Night’s Dream (William Shakespeare)

Henry V (William Shakespeare)

Public Enemies (?) More of a factual book, but still interesting, though the author's name escapes me

A Murder of Quality (John Le Carre)

Howl’s Moving Castle (Diana Wynne Jones)

The Secret Agent (Joseph Conrad)

Mary, Mother of Jesus – The Bible (I think that counts, as that would be what the film is based on)

Mio, My Son (Astrid Langden) A children's book, originally in Swedish, though I don't know if it's been translated

The Prince of Jutland / Royal Deceit was based on the Chronicles (of Saxo Grammaticus) which Shakespeare based his "Hamlet" on, but as the chronicles themselves are innaccessable (I haven't found them anywhere), Hamlet will have to do

Killing Pablo (Mark Bowden)

Also, there is a pick somewhere on this club which has most of these in it, but I guess you haven't seen it :)

Hope that helps!! It was actually pretty easy for me to answer this, as I have a word doc on my computer with alist of the books I want to buy on it .. I just added the ones I own and .. Presto!