Martin Edwards is well documented online so we'll confine our thoughts to personal experience and for the collector.
Collectors wishing to put together a full set of first edition books in dust jacket would do well to start their Martin Edward's collection now as they are disappearing into collections and many of the first edition hardback print runs, as usual in Britain, are modest with many going to public libraries.
Martin Edwards is firmly entrenched in the world of Crime Fiction and regularly attends associated events which means signed copies of his first editions are within reach. New collecotrs should check the publishers number lines, when applicable, to ensure first edition status.
There are also some excellent non-fiction reference books in Edward's bibliography: The Golden Age of Murder (2015), Taking Detective Fiction Seriously (2017) and The Story of Classic Crime in 100 Books (2017) - all of which are highly recommended.
DCI Hannah Scarlett and Daniel Kind in the Lake District Mysteries will be of particular interest to book collectors as the character Marc Amos is a rare book dealer who also has a bookshop in the Lake District and these books are peppered with references to collectable books which those of us who collect books will enjoy - a rare literary treat.
I've read the whole lake District series but, at the time of writing, none of the Harry Devlin books although I have read Gallows Court and it marks a departure for Martin Edwards it being set in the 1930s and is, in my opinion, the best book of his I've read.
Many authors forgotten by the public, though keenly sought by collectors, have seen the light of day once again thanks to Martin Edward's work with the British library reissues of Golden Age titles. These books have given readers a chance they once didn't have, the ability to read these books as many only exist in first edition form and even if they can be sourced are prohibitively expensive for the reader.