Let's see. I have "The Spice and Spirit of Kosher Cooking" and "Cooking Kosher the Natural Way", both of which were wedding gifts. Then I have 2 Passover cookbooks, and DD has one cookbook specifically geared for kids (which contains some good dessert recipes.)
Then there's the 6th cookbook that actually gets the most use. It's a looseleaf binder filled with recipes I've typed up- some from the internet, some from one of the other cookbooks, almost all with some tweaking from the original. This coming Passover, I may print up another copy of all my Passover-Friendly recipes and put them in a fresh binder, as I don't want my "year round" cookbook touching my Passover table.
I used to have a lot more cookbooks, but I gave most away as I didn't really use any of the recipes. The few I have are simple, basic cookbooks with recipes I'm likely to use often. The Spice and Spirit book happens to be a great resource- if I hadn't thought of typing up the most frequently used recipes, I'd need to replace it, as it's falling apart from heavy use. But in its current condition it will hold up as a reference book, any recipe I intend to use will get typed up and printed out. I may give away the "Kosher cooking the natural way" book, as it doesn't get much use anymore- but first I'll want to go through it and see if there's anything in there worth typing up. I used to find it a great reference as well, but now that I've learned more about traditional cooking methods and cut gluten out of my diet, much of the information is less relevent for me (either includes gluten, or isn't "natural" enough for me anymore.)
Maybe if I had more bookshelf space I'd feel differently about keeping a huge collection, but I'm in a small apt with literally 1 good bookshelf, plus 2 small ones that hold some children's books. I don't have a shelf in the kitchen for cookbooks- I don't even have the wallspace to put one up, and if I did I'd use the shelf for utensil and food storage! Decluttering the cookbooks means more room on the shelf for other books on other topics, and if we free up a whole shelf that means room for game storage or display space for photos or trinkets.