My favourite "cookbook" right now is a Word document called "favourite recipes" with a link to all my online resources, mostly YouTube videos (Pick Up Limes, Rainblow Plant life, ProHome Cooks, Yeung Man Cooking, Gaz Oakly, Ethan Cheblowski above all).
Physical cookbooks I still use:
The standard Bavarian cookbook that every household I know has (first edited in 1931 -
https://de.wikipedia.org/wiki/Bayerisches_Kochbuch) to look up basic things like ratios for Spätzle, how to cook a whole goose, classic potato dumplings and many other basics.
Hugh Fearnley-Whittingstall "Veg everyday", as a more
local, seasonal and compliant to my zone version of Yotam Ottolenghi's recipes (which I still love but eggplants are expensive, so are pomegranates, avocados and many ingredients he uses).
Then the "sourdough bible" by German baker Lutz Geißler if I don't want to improvise and look out for a special sourdough-ized recipe (muffins, panettone, pasta etc.)