I love cookbooks!
My most used is my Better Homes & Garden cookbook that I got as a wedding gift (and I have my mother's from the 1970s). I use those for general information on cuts of meat, types of grain, flour, beans, etc. I rely a lot on recipes from Fix It and Forget It crockpot cookbook, and I find new family favorites in my several Taste of Home cookbooks for soups/grilling/desserts/pastas.
But my treasured ones are: my grandmother's recipe box, my mom's recipe box and my childhood church's cookbook.
My best friend made a compiled cookbook of "tried and true" family favories (she asked several friends/family/coworkers to submit recipes). It's about 50 pages and has a variety of great recipes. I have been trying several.
I have about 30 cookbooks, most of them gifts or passed down from my mom and grandma. I do love church and organization's cookbooks as you get the tried and true favorites that everyone uses in their homes. I find those at thrift stores and garage sales, often for under a $1.