Can I start studying Logic with just some (informal) proof writing experience (worked through Velleman with supplemental exercises from other proof writing books like Eccles, Smith/Eggen/Andre, Bloch), but no experience in other rigorous mathematics (took a brainlet major, so now I'm self-studying)?
Would prefer a book focusing on natural deduction as proof system.
Some of the more standard books I looked at (namely Ebbinghaus, Rautenberg, Enderton) seemed way out of reach of my current skill-level.