I cook tons. I have ~100 cookbooks, a 1HP meat grinder, a deep fryer, a 75,000 BTU outdoor wok, a mangal, many fermenting vessels, hell a fermenting chamber for koji, and way too many knives. Someone at work asked about cookbook recommendations by country so here it is. There are many omissions to this list. It aims to be "if I wanted to get into X cuisine, what is the first cookbook I should buy to get started'.
General italian - Zuni cafe cookbook is a standout. Everyone says to get a copy of Marcella Hazen's Essential Italian but meh, I reach to zuni cafe way more often. Hightly recommended. Maybe Molto Mario or Babbo for a second or third italian book, but get zuni cafe first.
just pasta: flour + water
thai: the first pok pok cookbook is great (not the drinking food of thailand, not pok pok noodles) and super easy to get into. If that hooks you, Thai Food by Thompson is the bible, but muc harder to approach. Night+Market is also a good second book. (edited)