/sci/ - Science & Math

What are one or two good, affordable books on mathematical logic and/or set theory for a beginner? I'm planning on getting Naive Set Theory by Halmos since I've seen it recommended quite a bit and it's only $12, along with How to Prove it, but I can't find any books on mathematical logic that are under 50.

Why the fuck is this thread still up? What is wrong with you people? I've made multiple threads on /sci/ and the only fucking ones that gain traction and get to triple digit replies are the ones where I avatarfag with Kurisutina. Why?

>>11337768
/sci/ isn't
Every other board is filled with actual incels who are obsessed with cucking in one way or another. They manufacture a reality to fit their narrative that they could not have possibly succeeded in life. This is why they are all insecure rightwingers who can't go two seconds without talking about how I'd you're tall or have a big penis you win and if you don't you lose.

>planet called Earth
>is 75% water