Here is how Good Reads defines these mysteries

Cozies very rarely focus on sex, profanity or violence. The murders take place off stage, and are often relatively bloodless (e.g. poisoning), while sexual activity (if any) between characters is only ever gently implied and never directly addressed. The cozy mystery usually takes place in a small town or village. The small size of the setting makes it believable that all the suspects know each other. The amateur sleuth is usually a very likable person who is able to get the community members to talk freely about each other. There is usually at least one very knowledgeable, nosy, yet reliable character in the book who is able to fill in all of the blanks, thus enabling the amateur sleuth to solve the case.

 I would add that they often have a theme that they follow – cooking (complete with recipes), knitting (maybe even a pattern), book selling, house repairs, theater – it goes on and on.

The queen of traditional mysteries is Agatha Christie but lots of writers have followed in her path.  Here are a few suggestions:

 If you like to read about food and maybe even cook – Katherine Hall Page is a local author whose series about caterer Faith Fairchild has more than 20 titles – she has even put together a cookbook from the recipes included in each book.  Her latest is The Body in the Piazza. Here is a list of a few of her colleagues:

Peter E. Abresch – Elderhostel mysteries

M C Beaton – Agatha Raisin mysteries

Cleo Coyle – Coffeehouse mysteries

Diane Mott Davidson – Culinary mysteries

Katie Fforde – Second Thyme Around and Thyme Out

Joanne Fluke – Hannah Swensen mysteries

J. Lynne Hinton – Hope Springs Trilogy

Kay-Marie James – Cooking for Harry

G. A. McKevett – Savannah Reid mystery

Tamar Myers – Pennsylvania Dutch mysteries with recipes

Nancy Pickard & Virginia Rich – Eugenia Potter mysteries

Phyllis Richman – The Butter Did It and Murder on the Gravy Train

Linda Shepherd – Potluck Club mysteries

Lou Jane Temple – Heaven Lee mysteries and The Spice Box mystery 

 Knitting mysteries

Maggie Sefton has a series with 11 titles.  The first in the series is  Knit One, Kill Two.

Sally Goldenbaum’s latest in her knitting series is Angora Alibi: A Seaside Knitters Mystery

Other authors include Barbara Bretton, Rachel Herron and Gil McNeil

 To find more cozies (and more themes), check out a webpage that lists them by category and alphabetically – http://www.cozy-mystery.com/Cozy-Mysteries-by-Themes.html