Riding on the coat-tails, or plagiarism?

This is a question of continuing interest to me. Let me assure you it occurs in crime fiction, and murder mystery fiction, as in all other forms of writing.

Here is the Wikipedia definition, although I think this states the case rather more crudely than I am thinking of: Riding coattails is a metaphor that refers to the way in which lower level or uninspiring celebrities can often reach stardom through their ties to another, more popular and successful celebrity. This can often be used as a generic phrase for anyone that hangs onto another person as they forge ahead, without effort from the hanger-on.

Let me explain.

Last year I read A GENTLE AXE by R.N. Morris. ( I gave it 4.2)
Here is what I wrote:
St. Petersburg December 1866. An old woman foraging for whatever she can find discovers two frozen bodies in Petrovsky Park. One swings from the branch of a tree. In a large leather suitcase at his feet she finds the curled up body of a dwarf, his head split open as if with an axe. In his pockets she finds a pack of pornographic cards, a small key, and a bulging envelope of bank notes. Russia in 1866 is transforming itself into an industrial society, and the creation of a specialist department to investigate serious crimes is part of the transformation. Enter Porfiry Petrovich, newly appointed investigating magistrate for the Department of the Investigation of Criminal Causes. Author R. N. Morris has attempted to write not only a richly textured and authentic crime novel, but to do it in a style seen in writers like Dostoevsky, and more recently in the success of Boris Akunin. This is a world dominated by squalor, crowded tenements, poverty stricken students, and people who need to make a living however they can.
Morris has written A GENTLE AXE as a sequel to Dostoevsky’s CRIME AND PUNISHMENT. The clues are all there – the references to the earlier axe murders, to Raskolnikov, the detective is Porfiry Petrovich, the location in St. Petersburg, quotes from Dostoevsky and even a limited amount of direct acknowledgement. I missed realizing this because CRIME AND PUNISHMENT is not where I am coming from (40 years since I read it). The novel has caused quite a lot of comment in relation to plagiarism and identity theft, and Morris has joined quite a chain of writers who are continuing the work of the more famous. Recently he has published a sequel: A VENGEFUL LONGING.

Let's take a second, more recent case.
Recently Reginald Hill published A CURE FOR ALL DISEASES and I reviewed it (my rating 5.0).
Reginald Hill dedicated this novel "To Janeites everywhere". He says this novel has been ten years in the making, from seeds sown when he visited the Jane Austen Society's of North America's AGM. Reginald Hill wrote this novel not only for crime fiction readers, for those eagerly awaiting the next Dalziel & Pascoe, but also for those who know their Jane Austen.
My advice to you, dear reader, read everything.
You might like to check what he has done. Here is an earlier posting.
See also
http://en.wikipedia.org/wiki/Sanditon
http://www.pemberley.com/janeinfo/janewrit.html
http://tinyurl.com/4lenec
So is this taking the ideas of another, or a tribute to a master?
I would strenuously argue that what Hill has done is much harder than plagiarism.
Someone on the 4MA list has asked whether you need to check the Jane Austen connection to appreciate the book. My answer: if you understand what he has done in writing this book, then your appreciation of the book is heightened.

Just recently though, a fellow reader on the oz_mystery_readers list recommended Laurie King as a much under-rated, under-read author. The recommended book was THE BEEKEEPER'S APPRENTICE. Here is the blurb:
Set in 1914, a young woman, Mary Russell meets a retired beekeeper. His name is Sherlock Holmes, and he sees a fellow intellect in 15-year-old Mary, so takes her as his apprentice. Together, they tackle crimes and investigations, as Sherlock becomes Mary's mentor and friend.
Now I haven't read this yet, so can't really express an opinion, but it does seem to be me to be a bit like coat-tails riding.

But look, Laurie King is not on her own! Here are a couple that I know of:

ENTOMBED by Linda Fairstein My rating 5.0
Workers demolishing a nineteenth-century brownstone where Edgar Allan Poe once lived discover a human skeleton entombed -- standing -- behind a brick wall. When sex crimes prosecutor Alexandra Cooper hears about the case, it strikes her as a classic Poe scene...except that forensic evidence shows that this young woman died within the last twenty-five years. Meanwhile, Alex's old nemesis the Silk Stocking Rapist is once again terrorizing Manhattan's Upper East Side. The attacks soon escalate to murder, and the search leads Alex and detectives Mercer Wallace and Mike Chapman to the city's stunning Bronx Botanical Gardens. There, an enigmatic librarian presides over the Raven Society, a group devoted to the work of Poe.
This was an engrossing read. There's a lot of detail about Poe (and who knows if it is correct) but certainly we have all read some Poe at some time. I can believe too the claim made in the book that Poe was the originator of the detective novel. There were parts of the novel which were very Poe-ish in their macabre-ness and suspense.

THE AMERICAN BOY by Andrew Taylor
Blurb from Fantastic Fiction
Interweaving real and fictional elements, The American Boy is a major new literary historical crime novel in the tradition of An Instance of the Fingerpost and Possession. Edgar Allan Poe is the American boy, a child standing on the edge of mysteries. In 1819 two Americans arrive in London, and soon afterwards a bank collapses. A man is found dead and horribly mutilated on a building site. A heiress flirts with her inferiors. A poor schoolmaster struggles to understand what is happening before it destroys him and those he loves. But the truth, like the youthful Poe himself, has its origins in the new world as well as the old. The American Boy is a 21st-century novel with a 19th-century voice. It is both a multi-layered literary murder mystery and a love story, its setting ranging from the coal-scented urban jungle of late Regency London to the stark winter landscapes of rural Gloucestershire. And at its centre is the boy who does not really belong anywhere, an actor who never learns the significance of his part.

And there are many more. What do you know of? How do you feel about novels that are sequels to, or use the characters of, novels of already famous authors, or include fictitious renditions of famous people long dead? Am I being too picky? Does this practice muddy our knowledge of history - my guess is that is where I am coming from. Not a moral question at all, but rather how we will recognise the original ideas from the stuff that comes afterwards in the tributes and emulations. It is probably the same question as- if we take a historical setting and create a historical fiction, how we distinguish the real facts from the fiction. Or doesn't it matter?