My staple slow cooker cookbooks. This is what kicked off my ongoing cooking habit. I recommend the first one foremost as it's a good all around cookbook. Volume 2 is the 'easy prep' edition, so although there's a bunch more great recipes, there are some shortcuts taken that aren't necessarily ideal. In particular I am annoyed that it's started calling for onions by "cups" rather than number of onions, which is actually more work to track unless you're using frozen onions (I think they are, but I actually can't find any at any of my three local groceries and anyway onions are easy). The prep is never actually that onerous in any of the recipes in either. There is a third "healthy" one, which I also own but to be honest I don't think I've ever used it. And the Kindle formatting is progressively worse with each one, to the point that volume 3 doesn't even have a quick link to the table of contents.
Once I started branching out from the slow cooker, I took up
which is still a major staple for me. It has a huge range of great recipes, they're all quite easy and have variants and side recommendations (with the recipes for said sides at the back). It is impeccably organized and I LOVE the way it integrates the prep into the actual recipe in a way that a) makes best use of time and b) doesn't hide a bunch of extra work and time (the biggest amounts, usually) in the ingredient list the way most cookbooks seem to. Plus it's got technique tips and such interspersed throughout.
Once I picked up my dutch oven I started using some of America's Test Kitchen's other cookbooks, including
which is my most used because I love pasta, as well as
(because who doesn't love Mexican)
(this one gets a lot less use than Lost Suppers because over half the book is recipes for baked goods - cakes and pies, mainly. maybe someday, but I am not baking cakes or pies for one person. baaad idea.)
(so far mainly just Chicken Riggies, which are awesome as all hell, but a lot of other stuff looks good)
I haven't cooked from it in ages but I was also very impressed by https://www.amazon.com/dp/0811856240?tag=qt3-20
during an earlier cooking phase that didn't take nearly as well.
My current, excellent slow cooker (which has only been lightly used since my big slow cooker phase happened with my previous one, a CrockPot whose liner is now cracked): https://www.amazon.com/dp/B005MMNBDO?tag=qt3-20
This cutting board has been invaluable: https://www.amazon.com/dp/B000AAM0EY?tag=qt3-20
My excellent dutch oven: https://www.amazon.com/dp/B00U1OCPWQ?tag=qt3-20
My trusty skillet is a somewhat battered hand-me-down from my parents (who had to stop using it when they switched to an induction stove) so I highly doubt they still sell its exact model, but this seems similar: https://www.amazon.com/dp/B000NI6DMS?tag=qt3-20