If I read the book would I be able to figure out whats going

Well, you should be able to. Reading the book certainly can't do any harm, that's for sure.

Well, to a certain degree. Everyone should read the novel. It's great and I've read it many times, but it is only somewhat less confusing than the film for a couple of reasons. First, and most importantly, Raymond Chandler wasn't Agatha Christie. Tight plots were neither his forte nor even his intent. His writing was more about character, atmosphere, and dialogue (and, as in other elements, the movie is wonderfully faithful to this). Second, The Big Sleep was Chandler's first novel and loosely based on several of his earlier short stories. It wasn't cut and paste; he borrowed elements of the earlier stories and reworked them into the novel, but the joins fitting them together may show a bit. So the novel is also a bit confusing, but if you pay careful attention (and particularly if you read it several times) all the details of all the murders are laid out in the novel. Well, except, famously, that of the chauffeur.

What makes the movie even more confusing than the novel is the Production Code. The motivations for several of the murders (pornography, homosexuality, nymphomania) could not be depicted in the movie except, perhaps, in extremely vague allusions. Some of the details of the murders also violated the Code. Although the movie is generally quite faithful to the novel (aside from the omissions required by the Code and a far larger role for the Lauren Bacall character), the solution for Regan's murder offered in the last scene of the movie differs substantially from the book.

Raymond Chandler said that even he didn't quite understand everything about the plot.

I just saw it for the second time and the plot is impossible to follow without at least checking out its Wiki page.