This is a great film for anyone interested in Brian Wilson, whether you are a fan or not. It is very specifically focused on two eras in Wilson's life: mid-60s Pet Sounds/Smile (portrayed by Paul Dano), and late-80s Landy/first solo album (portrayed by John Cusack). The two time periods do not ever co-exist within the film except for one interpretation-hallucination scene towards the end. It is historically accurate from biographical accounts but it is presented in a way that you kind of get an idea of what Brian was feeling, seeing, hearing. It does jump back and forth between the two periods semi-frequently, and I have read this has caused some confusion amongst some viewers. Personally, I was able to follow along quite easily because I knew Brian's story before seeing this film. But even for someone not familiar with him, a viewer can pretty easily tell which time period is being portrayed simply by styles and sets (the 60s was vastly different looking from the 80s).
The only few, small things I have negative to say about the film are how they portrayed Murray Wilson (Brian's father), and some of the timelines aren't exactly right - but close enough to get the point across.
Murray Wilson is seen in the film as a very stern and abusive father, still very irked from The Beach Boys firing him as their manager and expanding their musical influences. While that really happened, I felt most of his character (based on the many biographies I've read) was over the top. Murray was a very competitive person, and he tried to make his sons competitive too (thus creating The Sunrays to compete with The Beach Boys' squeaky clean formula of the early 60s), but he was never vengeful towards them. They also feature a scene in which it is interpreted very easily by the viewer that Brian's deafness in an ear was caused by child abuse/slap from his father at a young age. While that has been speculated a few times by some biographies, it's never really been a proven fact. He could have just as easily injured himself, or maybe even had a physical problem that caused it. In summary, I think the character of Murray in the film doesn't show any love, and that just wasn't true of him - no matter how stern he really was or wasn't.
Timelines: Some of the timelines kind of break historical records, and I am sure this is for the purposes of dramatizing the film. For example, they suggest Brian started work on Good Vibrations as a direct response to the critical flop of Pet Sounds. In fact, Good Vibrations was being worked on as the album was being put together, and as Brian himself has mentioned before, was actually meant for release as part of Pet Sounds. But with the record company pushing the release of new (overdue) material and Brian not yet satisfied with the pieces of Good Vibrations, it got left off the album. They released it as a desperation single in advance of Smile to try and bring The Beach Boys back onto the charts once more - and that it did...their #1 best selling single ever.
Other than those few things, I think the film is a great watch and artistic vision of one of the greatest musical composer's life we will ever see. Watch it, buy it, enjoy it!