The thing about Brennan's gho$twritten book (that was published some time after his death, and therefore wide open to 'enhancements' at the whim of the writer, despite Brennan, apparently, signing-off on the original manuscript), is that in said book 'Brennan' wafts poetically about his or soul (or something) in describing the red plume (or something) around Kennedy's head.
The trouble is that in testimony, IMS, Brennan said he was unable to see Kennedy during the head shot, that an obstruction of some sort blocked his view.
The book was written with the help of the reverend J. Edward Cherryholmes. It is mostly about how the assassination and its aftermath affected Howard Brennan for the rest of his life. I would definitely say the earlier testimony and affidavits of Brennan should carry more weight than this book.
Two things about the description of the three shots in the book don't ring true. First, Howard Brennan testified to the WC he didn't remember hearing the second shot. Secondly, In a quick scan, I didn't find anything in his WC testimony about whether or not he saw JFK when the head shot hit. However, it does appear to me that the tall concrete structure and a tree would have blocked his view of JFK at that instant.