The rules: All novels must have been originally written before 1960 and be from the mystery category (crime fiction, detective fiction, espionage, etc.), and each book may only count for one category. Once you have met the 8 book minimum, you may repeat any category (except the last one) any number of times to reach the 16+ level.
An added bonus to joining in the challenge is this: Everyone who completes the 8 book minimum will be entered for a prize drawing at the end of the year. Anyone who completes 16 or more books will automatically receive their choice from a prize list.
Grey Mask (1928) by Patricia Wentworth (May 2013)
8 Faces at 3 (1939) by Craig Rice (June 2013)
A Murder is Announced (1950) by Agatha Christie (January 2013; solved by Miss Marple.)
The House without a Key (1925) by Earl Derr Biggers (July 2013)
A Pocketful of Rye (1953) by Agatha Christie (February 2013/audio)
The Black Thumb (1942) by Constance and Gwyneth Little (June 2013)
Dead Men Don't Ski (1959) by Patricia Moyes May 2013; set in the Italian Alps)
The Mouse in the Mountain (1943) by Norbert Davis (July 2013))
9. A Calendar of Crime: a mystery with a date/holiday/year/month/etc. in the title
The Frightened Wife and other murder stories (1953) by Mary Roberts Rinehart (September 2013/audio)
Who Killed the Curate? (1944) by Joan Coggin (May 2013)
Sparkling Cyanide (1945) by Agatha Christie (August 2013)
The G-String Murders (1941) by Gypsy Rose Lee (August 2013)
The Penguin Pool Murder (1931) by Stuart Palmer (July 2013)
The Patient in Room 18 (1929) by Mignon Eberhart (June 2013; involves theft as well as murder)
The Yellow Streak (1922) by Valentine Williams (May 2013)
The Secret of Chimneys (1925) by Agatha Christie (June 2013/audio)
The After House (1914) by Mary Roberts Rhinehart (March 2013; takes place on a yacht)
The Red Trailer Mystery (1950) by Julie Campbell (July 2013; refers to a travel/camper trailer)
Death at the President's Lodging (1936) by Michael Innes (August 2013)
21. Things That Go Bump in the Night: a mystery with something spooky, creepy, gothic in the title
The Secret Adversary (1922) by Agatha Christie (June 2013/audio) This was the first Christie I read, many years ago, and started my love for her novels; it's fun to reread old favorites.
Why Kill the Butler? (1933) by Georgette Heyer (June 2013)
The Norths Meet Murder/Mr and Mrs North Meet Murder (1940) by Frances and Richard Lockridge (June 2013)
Partners in Crime (1929) by Agatha Christie (July 2013/audio)
26. Size Matters: a book with a size or measurement in the title
The Black-Headed Pins (1938) by Constance and Gwyneth Little (May 2013) It includes a seance--granted one that turns into a comedy, this is a Little novel after all--and suspected supernatural actions.
The Moving Finger (published in 1942) by Agatha Christie (January 2013/audio; television movies 1985 and 2006.)
The Case of the Velvet Claws by Erle Stanley Gardner (July 2013)
The Adventures of Sherlock Holmes (1892) by Sir Arthur Conan Doyle (September 2013)
31. Killed in Translation: Works that originally appeared in another language and have been made available in English (works published in English post-1960 would be acceptable, provided the original was published pre-1960).
32. Blondes in Danger: A variation on "Colorful Crime". Books that feature a blonde in the title role.
The Barakee Mystery (1929) by Arthur Upfield (July 2013; Austrailian)
The Thirty-Nine Steps (1915) by John Buchan(July 2013/audio; reviewed by Past Offenses)
Murder by Experts (1936) by Anthony Gilbert, pseudonym for Lucy Beatrice Malleson (June 2013)
N or M? (1941) by Agatha Christie (July 2013; knitting nearly gets Tuppence in trouble, plus the spying is a hobby of sorts for the Beresfords)
The Chief Legatee (1906) by Anna Katherine Green (January 2013) This is the oldest mystery I have read to date (June 2013). It is also notable for being the most convoluted that I have read thus far. I'll admit though, that despite the Gothic/Romantic plot themes and the fact that this wasn't Green's best, I did rather enjoy it.
I slightly condensed some of the category descriptions for the sake of space; please go to the original site to see full description of each category.