The Accident of Robert Luman was published in 1988. The author, David Fletcher (a pen-name for Dulan Barber) died in the same year. He was only 48. Fletcher's tragically early death probably explains why his work has been neglected in recent years. Another reason for that neglect is that he didn't create a major series character (although this novel introduces a cop called DS Jolley, who appeared in Fletcher's last two novels). He was a well-regarded novelist in his day, but I'm pretty sure that he'd have developed further had he lived, and he might well have become a doyen of the genre.
This novel is interesting on several levels. First, it's a "whowasdunin". An introductory section reveals that a murder of extraordinary savagery has been committed - but we don't know the identity of the victim. This aspect of the story is intriguing, though it's not Fletcher's main focus - and I think it's fair to say that the victim isn't characterised in great depth, a weakness of the story.
Second, it's a novel of psychological suspense, a gripping tale which reads in some respects like an updating for the 80s of the work that John Bingham and Julian Symons were doing twenty or thirty years earlier. Fletcher builds the tension as he shows a young man being trapped in a web of suspicion. In fact, in some respects, this book is a development from his previous novel, On Suspicion - but it's a superior work.
And one of the reasons why it's superior is that Fletcher presents a very interesting picture of a brain-damaged character, Robert Luman himself. I'm not sure that I can think of an earlier, more convincing portrayal of a character with a severe mental disability - if you can, please let me know! In recent years, several authors have tackled a comparable challenge with great success: one thinks of books like Elizabeth is Missing and The Curious Incident of the Dog in the Night-Time. Fletcher's novel is not quite as impressive as either of those two books, but I thought it a highly readable piece of work.