John Dickson Carr (1906-1977), among the crime novelists I grew up reading, is the best of the best. US-born but with close ties to the UK, Carr is one of the stars of the Golden Age of crime fiction.
And now you can read him in ebook format. Thanks to the Langtail Press, six of Carr's classic novels are now available--all 'contemporaries', most featuring one or the other of his star detectives, Dr. Gideon Fell (He Who Whispers, The Problem of the Green Capsule) or Sir Henry Merrivale (The Plague Court Murders, And So to Murder, She Died a Lady), with one spectacular non-series novel, The Burning Court, thrown into the mix. (I've provided links to Kindle editions, but all six are also available on iBooks, and Carr is 'priced to sell' in both formats.)
And just in case you're not a fan of locked-room puzzles... neither am I: I just like John Dickson Carr.
Give him a try.