Anyone who spends years of their own time researching this subject deserves a great deal of respect.
Matthew Smith's theory is very plausible, not at all far-fetched. Clearly he has put a great deal of thought into this, and I will certainly read his other books on the same subject.
What makes this book stand out is that it is not simply a re-hashing of other people's theories, nor does it just focus on the failings of the Warren Report and the U.S. government (although his criticisms are well-founded and balanced). Where other books have thankfully stripped the official version of any credibility and raised serious questions, Matthew Smith goes a step further and says "this is what I think might have happened..." The second half of the book provides an excellent chronological account of Lee Harvey Oswald as an adult and shows very simply how he became involved in JFK's assassination.
The book itself, however, is at times badly written. Occasional poor sentence structure often causes the reader to stumble at a key stage. Smith also at times does not make clear whether he is writing about a documented fact or personal opinion. More noticeable is a tendency to repeat statements at curious times, or interject thoughts at random moments, particularly so in the last 2 pages: Smith is discussing the merits of a note allegedly written by Oswald to a "Mr Hunt", but this quickly moves into a 4-line conclusion to the book.
Don't let that put you off though - it really is worth reading.