I struggled with this same thing for ages, but now I have my system down:
- When I get a new cookbook, I attach a piece of paper to the inside cover, on which I write all the recipes I want to try from it, divided into categories (mainly in terms of 'less than an hour' / 'more than an hour', since that defines whether I can make them on a weeknight after work or not) but also sometimes other categories as well eg 'breakfast' / 'sides' / 'desserts' etc.
- I then go to EatYourBooks and bookmark all those recipes with 'I want to make this'
- When I make a recipe, I tick it off on the paper with a brief note eg 'delicious', 'meh', 'not good' (to help future me remember whether it's worth making again), and also change the bookmark in EatYourBooks to 'I've made this' and/or 'Favourite recipes' and add some notes and maybe a photo.
- I plan all my cooking a week in advance. Once a week I sit down and plan out what I'm going to make on every night, based on some combination of a) wanting to cook from a particular cookbook or b) what I have in the freezer/fridge/pantry that needs using up (this is where EYB really comes into its own) and c) how much time I'll have on a given day. I do all the shopping based on those recipes I want to make, so I have everything for that week to hand.
In terms of deciding which books to use when you have so many: I recently decided that I would make three recipes from each of my existing cookbooks before moving onto new ones, which has worked out well and forced me to make some dishes that I would probably otherwise never have got round to.